Rachel Laudan

We have just one cookbook from the Roman Empire and it’s always known as Apicius. For a long time the author was thought to be a great gourmet. No, say Christopher Grocock and Sally Grainger in their invaluable translation. A cook or a series of cooks just jotted down the minimum they needed to remember a recipe. Just an ancient version of those crammed boxes of notes in your mother or grandmother’s kitchen.

That means the manuscript is full of puzzles. One is the white sauce for boiled bird. But except for the fact that it is white it has nothing to do with modern white sauce. Here’s the recipe.

“Pepper, lovage (a herb), cumin, celery seed, roasted hazelnuts or almonds or (any) skinned nut, a little honey, liquamen (like contemporary Thai fish sauce) vinegar and oil.”

No instructions! The cook was supposed to know what to do. In all likelihood he (we’re talking professional cooks here) pounded the spices, herbs and nuts, and then stirred in the liquid ingredients.

The puzzle is the phrase “any skinned nut.” Latin, unlike English, does not have a single word for nut. Here the word is nuces. It can refer to walnuts but how could these be skinned (as opposed to shelled) and how could they be put in a white sauce? If you’ve ever eaten walnuts you know the problem. The skin is glued to the nut. And grinding them would give a brownish paste.

So here’s a little detective puzzle. And, I think, Mexican cooking can shed light. Just look at this photo.

On the left is the kind of walnut you usually buy in the store. Old and dry. On the right is a walnut (often called nuez de castilla or Spanish nuez) sold in a Mexican market. It’s young, fresh, soaked in water, and someone has peeled off the skin while it’s still possible to do so–that is in September just when they ripen. It’s tedious, fiddly work which is why they cost $10 a pound. In short, it’s quite possible to peel walnuts but only when they are super fresh.

And they are sheer delight. They have almost the consistency of water chestnuts, slightly crunchy with a a very slight and appealing bittenerness. They are “gourmet” items in Mexico. And they are used to make a wonderful white sauce. The little flyer given out in the San Angel market in Mexico City offers these instructions which I’ve translated.

100 grams of nuez de castilla, peeled and without the brown skin

1/2 can of fresh crema (that is, about a cup of creme fraiche)

1 teaspoon of sugar

Salt to tste

Put all these ingredients in the blender and whiz together.

This makes a shining whiter-than-white sauce. It’s spectacular looking and spectacular to eat.

It’s spooned over stuffed poblano chiles to make one of Mexico’s signature dishes. But that’s another story. And so is the question whether there is or is not any connection between the sauce of ancient Rome and the sauce of today’s Mexico–I bet yes, but that’s another story too.

This story is whether or not it’s possible to make a white sauce with walnuts. Answer, a resounding yes.