The Salad That Teaches What Nut and Seed Oils Are For
Filed under Olive Oils
Walnut oil has a particular fate in American kitchens: bought for one recipe, used once, moved to the back of a cupboard, and rediscovered a year later smelling faintly of an art classroom. The bottle was never the problem. The problem is that toasted nut and seed oils get sold as cooking oils when they behave more like spices, and nobody tells the cook that the whole point is the pour. One salad fixes this. It takes twenty-five minutes, it comes out of the walnut country of southwestern France, and it teaches the move that works for every bottle in the family: walnut, hazelnut, and the green-black pumpkin seed oil of Austrian Styria.
The flavor of these oils is made in the roaster, before a press ever touches a nut. Producers toast walnuts, hazelnuts or hulled pumpkin seeds until browning chemistry builds aromas the raw nut only hints at, then press the warm paste; mills like La Tourangelle, roasting in cast iron kettles the way French oil mills have since the nineteenth century, still work on exactly that principle. What comes out is the roasted nut in pourable form. It is also fragile. Nut oils run high in polyunsaturated fat, which is part of why they taste so lively and all of why they stale quickly. The roasted aromas that justify the price are volatile; a hot pan sends them into the kitchen air rather than onto the plate. Harold McGee's guidance in On Food and Cooking is blunt about the consequences: keep these oils cold, and use them raw.
Two rules follow, and they carry the whole category. First, the oil belongs in the pour, never the pan. When the pan is hot you want butter or an olive oil suited to heat, a distinction the olive oil buying guide spells out; the nut oil arrives once the heat is off, spooned over finished food the way you would use a fine vinegar. Second, the echo rule: a nut oil is loudest next to its own nut. Walnut oil over toasted walnuts, hazelnut oil over crushed roasted hazelnuts, pumpkin seed oil under a scatter of toasted seeds. The oil supplies the low roasted hum, the whole nut supplies the crunch, and each makes the other read as twice itself.
Why this salad
Noix de Grenoble has held its appellation since 1938, and the Dordogne is so identified with the crop that its winter salad is simply leaves and walnut oil. Paula Wolfert recorded the habit in The Cooking of South-West France: bitter greens, a walnut oil vinaigrette, toasted walnuts, sometimes cheese. The logic is worth stealing outright. Walnut oil is faintly tannic and a little austere, so it wants leaves with their own bitterness, an acid gentler than red wine vinegar, something sweet to bridge (the pear), and, if you like, something salty and loud (a blue cheese). Nothing on the plate is decoration; every part is holding a corner.
The vinaigrette runs at the classic three parts oil to one part acid, the ratio the house dressing piece builds everything on, and it leans on a teaspoon of Dijon, which holds oil and vinegar together for reasons the emulsion piece explains. Sherry vinegar is the traditional partner. A white balsamic condiment is a softer one that flatters the oil instead of fighting it. The half teaspoon of honey is not there as sweetness you can name, just to round the bitter edge of the leaves.
Ingredients
- 2 heads Belgian endive
- 1 small head frisée, or half a head of escarole
- 1 small head radicchio
- 1 cup (100 g) walnut halves
- 1 firm ripe pear, or a crisp apple
- 3 oz (85 g) Roquefort or an aged goat cheese, crumbled (optional)
- 3 tablespoons toasted walnut oil
- 1 tablespoon sherry vinegar, or a white balsamic condiment
- 1 teaspoon Dijon mustard
- 1/2 teaspoon honey
- Fine sea salt and black pepper
- Flaky salt to finish (optional)
Method
- Toast the walnuts. Spread them in a single layer on a sheet pan and toast at 350°F for 8 to 10 minutes, until they smell strong and have gone one shade darker. Slide them off the hot pan the moment they come out, since carryover heat on the metal keeps toasting them, and cool completely. The judgment here is the same one that makes good bar nuts: fragrant and a shade darker, never two.
- Make the vinaigrette. Whisk the mustard, vinegar, honey and a pinch of salt in a small bowl, then whisk in the walnut oil in a thin stream until the dressing tightens slightly. Taste it on a leaf, not a spoon, and adjust; a dressing destined for bitter greens should taste a touch too sharp on its own.
- Prepare the greens. Wash the endive, frisée and radicchio, dry them thoroughly, and tear them into fork-sized pieces. Slice the pear thin just before serving so it does not brown.
- Dress the salad. In a large bowl, toss the leaves with about three quarters of the vinaigrette until every surface shines, then add the pear and toss once more, gently.
- Plate and finish. Divide among plates, scatter the walnuts and cheese over the top, spoon a little of the remaining vinaigrette over each, and finish with black pepper and a pinch of flaky salt.
Nothing in this salad answers to altitude; a 350°F oven toasts nuts the same at 5,280 feet as at sea level. The one variation below that involves boiling water gets its own Denver note.
Why it went wrong
| Symptom | Cause | Fix |
|---|---|---|
| Dressing slides off the leaves | The leaves were wet | Dry them until a leaf pressed to your palm leaves no water behind; a damp leaf sheds vinaigrette |
| Salad tastes flat | The vinaigrette was seasoned on a spoon | A dressing that tastes balanced on a spoon reads mild across a bowl of greens; sharpen with vinegar and salt, then retest on a leaf |
| Harsh, scratchy bitterness | Over-toasted nuts, or oil past its prime | Nuts go one shade darker only; fresh walnut oil smells like the nut, so taste the oil from a spoon before it goes in the bowl |
| Dressing broke into slicks | Oil added all at once, or no mustard | Start over with the mustard and a few drops of water in a clean bowl and whisk the broken dressing back in slowly |
| Oil smells like crayons or paint | Oxidation | That bottle is past saving on a salad; going forward, refrigerate after opening and buy sizes you will finish within a few months |
The other two bottles
Hazelnut oil, the sweet one
Where walnut oil is tannic, roasted hazelnut oil is round and almost pastry-like, which points it at sweet vegetables rather than bitter leaves. The dish to make is beets: roast them whole until a knife slides in, peel and slice them warm, season with sherry vinegar and salt, then dress with hazelnut oil and finish with crushed toasted hazelnuts and goat cheese. Warm blanched green beans take the same treatment, and so does roasted winter squash. The echo rule does heavy lifting here, because hazelnut oil plus toasted hazelnuts lands close to the flavor of brown butter, with the same roasted sweetness carried in a pour instead of a pan. Anyone who has eaten through Piedmont in hazelnut season knows how far that register can go.
Pumpkin seed oil, the Styrian one
Styria, in southeastern Austria, grows a pumpkin whose seeds carry no hull, a chance mutation that appeared there toward the end of the nineteenth century and turned the region into pressing country. The seeds are roasted and pressed into an oil so dark it pours nearly black, protected since 1996 as Steirisches Kürbiskernöl PGI. It is also a party trick of physics: poured thin across a white plate it reads deep green, while the bottle itself looks red-black, and it is the example scientists reach for when they explain dichromatic color (Kreft and Kreft measured exactly this in 2007). Few dinner-table facts can be demonstrated with a plate.
The Styrian uses are the ones to copy. First, warm potato salad: simmer waxy potatoes in their skins until a knife meets no resistance, about 15 to 20 minutes at sea level, then slice them warm and dress with cider vinegar, a spoonful of the warm cooking water, minced shallot and salt, and pour the pumpkin seed oil over generously, with toasted pumpkin seeds on top. In Denver, water boils near 202°F rather than 212°F, per Colorado State University Extension, so start checking closer to 20 minutes and trust the knife rather than the clock; the altitude guide covers why. Second, and this one sounds like a dare: across Styria the oil is poured over vanilla ice cream, where it eats like a roasted, malty butterscotch. Both uses keep the oil far from heat, which is where the producers themselves insist it stay.
Which bottle, which plate
| Bottle | Its register | Reach for it with | The classic |
|---|---|---|---|
| Walnut | Tannic, austere, faintly bitter | Bitter greens, lentils, the cheese course | The salad above |
| Hazelnut | Round, sweet, brown-butter adjacent | Beets, green beans, squash, goat cheese | Warm beets with hazelnuts |
| Pumpkin seed | Dark, resinous, malty | Potatoes, cream, soft cheese, vanilla ice cream | Styrian potato salad |
The taxonomy compresses to a sentence: walnut to bitter, hazelnut to sweet, pumpkin seed to starch and cream, and every bottle near its own toasted nut.
Keeping the bottles alive
Refrigerate all three once opened and think in months, not years; the cloudiness cold causes is harmless and clears at room temperature. Buy small. The label needs only two things: the word roasted and a date you can actually find. And there is a reason the stale bottle smells like an art classroom. Walnut oil is a drying oil, one that sets by reacting with air, which is why Renaissance painters bound pigment with it; period writers, Vasari among them, favored it for whites and blues because it yellows less than linseed, and conservators still find it in Italian paint layers. The same eagerness to react with air that cures a painting is what stales a forgotten bottle. That is the entire storage argument in one image, and it is a better story than most of what gets said over a salad.
The Ambrosian Pantry is at 263 Josephine Street in Cherry Creek, Denver, and ships across the continental U.S. from theambrosianpantry.com. If any bottle or vinegar in this piece raises a question, come in and ask; questions are what the staff is there for.
Make the salad once and the rest of the family stops being mysterious, because every bottle wants the same two courtesies, a cold shelf and a finished plate. The next time someone at your table asks about the dressing, hand them the bottle, cold from the fridge, and tell them about the painters.
Sources & Further Reading
- Harold McGee, On Food and Cooking: The Science and Lore of the Kitchen (Scribner, 2004), on nut oils, oxidation and cold storage
- Fruhwirth and Hermetter, "Seeds and oil of the Styrian oil pumpkin," European Journal of Lipid Science and Technology 109 (2007)
- Kreft and Kreft, "Physicochemical and physiological basis of dichromatic colour," Naturwissenschaften 94 (2007)
- Gemeinschaft Steirisches Kürbiskernöl g.g.A. and the EU register entry for Steirisches Kürbiskernöl PGI
- Comité Interprofessionnel de la Noix de Grenoble and INAO records for the Noix de Grenoble appellation
- Paula Wolfert, The Cooking of South-West France (revised edition, 2005)
- Colorado State University Extension, high altitude cooking guidance
- National Gallery Technical Bulletin, analyses of oil paint media in Italian Renaissance painting
- The Pantry Dispatch: La Tourangelle producer guide
- The Pantry Dispatch: The Vinaigrette Ratio
