Cold Peanut Soba: The Nut Butter Sauce Worth Learning First

A jar of good peanut butter is a sauce base before it is a spread. It is roasted nuts ground to a paste, rich in fat and protein, and it needs a few things to become something you pour: salt, acid, a little sweetness, a second fat for aroma, and hot water. This recipe whisks those parts together in one bowl and pours the result over cold buckwheat noodles. The sauce is done by the time the water boils. The noodles take less than ten minutes. Learn this one first, because satay and a peanut dressing for slaw run on the same method with different seasonings.

The surprise comes when the water goes in. The first spoonfuls make the paste tighter and grainy, as if it has broken. It has not. Keep whisking and keep adding water a spoonful at a time, and the paste relaxes into a smooth, glossy sauce about the thickness of heavy cream. Tight first, loose after: that is the cue, and once you have seen it the measuring spoons become optional.

Ingredients, for four

For the sauce

• 160 g (2/3 cup) peanut butter, crunchy or smooth, stirred well. A roaster's jar like Big Spoon Roasters Crunchy Peanut Butter (shop Big Spoon Roasters Crunchy Peanut Butter) gives the sauce texture
• 4 tablespoons soy sauce
• 3 tablespoons rice vinegar
• 1 1/2 tablespoons toasted sesame oil
• 1 1/2 tablespoons honey
• 1 small garlic clove, finely grated
• 2 teaspoons fresh ginger, finely grated
• 6 to 8 tablespoons hot water, from the kettle or the noodle pot

For the bowl

• 500 g dried buckwheat soba, two packages of buckwheat soba (shop buckwheat soba)
• 1 English cucumber, cut into matchsticks
• 3 scallions, thinly sliced
• 1 tablespoon toasted sesame seeds
• 2 to 4 teaspoons chili crisp
• A handful of roasted peanuts, chopped, and lime wedges (both optional)

Method

1. Start the water. Bring a large pot of water to a full boil. Leave it unsalted; the soy sauce seasons the whole dish.
2. Make the paste. In a mixing bowl, whisk the peanut butter, soy sauce, rice vinegar, sesame oil, honey, garlic and ginger together. It will be thick and heavy, closer to frosting than to sauce. That is correct.
3. Loosen it with hot water. Add hot water one tablespoon at a time, whisking after each. For the first two or three spoonfuls the paste tightens, turns dull and may look split. Keep going. Somewhere around the fourth or fifth spoonful it turns smooth and glossy. Stop when it pours off the whisk in a ribbon, like heavy cream. Taste it: salty, a little sharp, a little sweet, and clearly roasted peanut.
4. Cook the soba. Drop the noodles into the boiling water, stir them apart for the first thirty seconds, and cook according to the package, usually four to six minutes. Taste a strand a minute before the package time. It should be tender all the way through with a little spring.
5. Rinse cold. Drain the soba into a colander and rinse under cold running water, rubbing the noodles gently between your hands until the water runs clear and the noodles are cold. Shake the colander hard; wet noodles thin the sauce.
6. Toss. Add the noodles to the sauce bowl with about three quarters of the sauce and toss with tongs or chopsticks until every strand is coated. If the sauce grips too tightly, add a splash of cold water and toss again.
7. Finish. Divide into bowls, spoon the remaining sauce over the top, and scatter on the cucumber, scallion, sesame seeds, chopped peanuts and a spoonful of chili crisp with some of its oil. Serve with lime on the side.

The ratio behind it

The sauce is five parts, and each has a job. The nut butter is the body and the fat. The soy is the salt and the savory depth. The vinegar is the acid that keeps a rich sauce from tasting heavy. The sesame oil is there for aroma more than fat. The honey rounds off the edges of the salt and the acid. By volume it works out close to seven parts nut butter, two and a half parts soy, two parts vinegar, and one part each sesame oil and honey, with hot water added until it pours. Change the jar, keep the proportions close, and adjust the seasoning to what the jar brings.

Stir the jar before measuring. A natural nut butter separates, with oil rising to the top, and a spoonful from the top is mostly oil while a spoonful from the bottom is mostly dry paste. Either one throws off the ratio. The federal standard for anything labeled peanut butter allows seasoning and stabilizing ingredients up to ten percent of the finished weight and caps fat at fifty-five percent. A jar that stays smooth on the shelf usually has a stabilizer; a jar that separates usually has little beyond peanuts and salt. Both make this sauce.

Swapping the jar

Why it went wrong

Notes and variations

In Denver, the noodles take a little longer. Water boils at 212°F at sea level, and the boiling point drops about one degree for every 500 feet of altitude, which puts a Denver pot at roughly 202°F. Foods cooked in water take longer at that temperature, so taste the soba at the package time and expect to give it one or two more minutes. The sauce needs no adjustment. The rest of the altitude adjustments are in cooking at altitude.

Make ahead. The sauce thickens as it chills; loosen it with a spoonful of hot water before using. Dressed noodles are best within a few hours, since the soba soaks up the sauce as it sits.

Make it dinner with shredded cooked chicken, cubes of firm tofu, or a soft-boiled egg halved on top. The same sauce works as a dip for raw vegetables and summer rolls, thinned as a dressing for shredded cabbage, or brushed on grilled chicken skewers in the last minute. The chili crisp guide covers the jars that finish the bowl.

The sweet side of the jar. The same peanut butter makes the other classic, in the how to make the best peanut butter and jelly guide, and the guide to jam, preserves and marmalade handles the fruit half. The bar nuts guide covers roasted nuts eaten whole. The roaster behind three of the jars above is profiled in the Big Spoon Roasters guide.

The peanut butters and buckwheat soba are at 263 Josephine Street in Cherry Creek, Denver, and ship nationwide from theambrosianpantry.com.

Sources & Further Reading

• New Mexico State University Cooperative Extension, Guide E-215: High-Altitude Cooking
• 21 CFR 164.150, Peanut Butter: the federal standard of identity
• The Pantry Dispatch: Why Nut Butter Separates, When It Turns, and Where to Keep It
• The Pantry Dispatch: Cooking at Altitude