If you visit an Italian supermarket today -- anywhere in Italy -- you'll find an aisle dedicated to olive oil. All kinds, from olio di sansa -- "olive" oil made through industrial processes, which is marginally suited to cooking, through virgin, which can be quite nice and is ideal for cooking, with a high smoke point that makes it good for frying too, and on to extra virgin, which is perfect for seasoning salads, making bruschetta, or drizzling over hearty soups.
You probably won't find walnut oil.
And this is a pity because it can be very good.
"Why walnut oil? I thought Italy is the land of the Olive Tree," I hear you say.
Much of Italy is the land of the olive tree; it grows very well in the south, with trees so large I mistook them for scrub oaks the first time I saw them, and though the trees are smaller further north, they do grow as far as Liguria, Tuscany, and Umbria, and produce spellbinding oils.
Olive trees don't do so well north of the Apennines, however: Though the Romans did try to introduce them, they succeeded in growing them only in well-protected spots, and never produced enough olives to make olive oil production a viable activity.
As a result, olive oil is conspicuously absent from the traditional cooking of Northern Italy -- people used animal fats, or if they could afford it, butter. And had to come up with something else to use as a condiment, for example over salads or soups.
Walnut oil is a logical choice: walnut trees grow quite well in the colder northern climates, and the oil from the nuts is delicately walnut-flavored, rich in minerals, and easy on the digestion.
In Northern Piemonte, because of its isolation, walnut oil was especially prized, and indeed stands of walnut trees were one of the characteristic features of the landscape, while the crop was important enough that, in the Middle Ages, towns punished those who snuck into groves to pick up fallen walnuts, and also imposed transport duties upon both walnuts and walnut oils.
The walnut harvest took place in autumn: People gathered together to pick the nuts, which were then dried, shelled, and ground; the resultant nut flour was heated, and then pressed to extract the oil.
It was a communal activity, with families or neighborhoods helping each other work through their stands of trees.
And, as is often the case with communal activities, walnut oil production played a social function, helping cement both families and neighborhoods. Unfortunately, the oil does have several drawbacks, the foremost being the high cost of making it -- even if people weren't paying for it, they were still putting in the time. The other two are related more directly to the oil:
- Walnut oil has a very low smoke point, which means that it cannot be used for frying, and is not too suitable for cooking either.
- Walnut oil lacks the antioxidants one finds in olive oil, and as a result, will keep a year at most before becoming rancid in an unopened container, and for a month or two if kept in a cool dark place after the container is opened.
For these reasons, when the price of olive oil -- which had always been available, though it was very expensive -- dropped in the mid-20th century, walnut oil fell into disfavor and production in areas like Northern Piemonte decreased drastically.
But it never vanished completely, and now there is renewed interest in it on the part of lovers of traditional foods and those interested in preserving traditional ways of life; in particular, the Province of Biella is trying to revive it and held a presentation dedicated to walnut oil at Slowfood's Salone del Gusto.
Before we get to the recipes, a couple of words about purchasing walnut oil: Since it is perishable, you should buy small amounts, and check the container before purchasing it to make certain that it's not more than a year old.
If you live in Europe, the Province of Biella was pouring an oil made by a farm called Oro Di Berta.
If you are elsewhere, check a good delicatessen or health food place. Or check the web; Google turned up a number of suppliers, in North America and elsewhere.
One thing to be wary of is oils that are overly cheap; since making walnut oil is a labor-intensive process, something that is overly cheap may have been made by cutting corners.
Don't know about walnut oil? Background. Got some? Ideas:
The most classic use, says Mina Novello, who has published a booklet of walnut oil recipes, is to drizzle it over salads, cooked and raw vegetables, soups (especially hearty soups or minestrone), grilled meats or fish, mild cheeses, and in Bagna Cauda, the rich garlicky sauce that is a symbol of Piemontese conviviality.
The Bagna Cauda Biellese does differ some from what's made in southern Piemonte. You'll need:
8-12 large cloves of garlic, peeled and green parts removed
A scant half-pound (200 g) first-rate salted anchovies
A cup of milk
1/4 cup (50 g) unsalted butter
1/2 cup olive oil
5-6 tablespoons walnut oil
Put the cleaned garlic in a small pot, ideally terracotta, with milk to cover and cook it over a very gentle flame until the milk has evaporated and the garlic is very soft.
While it is cooking, rinse the salt from the anchovies, scale them, split them, and bone them. Chop them finely.
Squash the cooked garlic with the tines of a fork, and mix the olive oil into it, together with the butter, and heat the mixture over a very gentle flame. Stir in the anchovies, shifting them about with a wooden spoon to break them up, stir in the walnut oil, and continue heating over a gentle flame -- you want the sauce hot, but do not want the garlic to fry, because if it does it will ruin the sauce.
At this point your bagna cauda is ready; serve it with a mixture of sliced cooked and raw vegetables, including cabbage leaves, carrot sticks, celery sticks, bell peppers both raw and cooked, fresh artichokes, spring onions, onions, and whatever else suits your fancy.
One can do other things as well. For example:
Make mayonnaise, using a mixture of walnut oil and peanut or sunflower seed oil instead of olive oil, and seasoning the mayonnaise with a teaspoon of finely chopped lemon balms (Melissa officinalis), or the herb of choice.
Season pasta: One of the classic Ligurian sauces for ravioli is a creamy sauce made with walnuts; you can also use walnut oil, salt, pepper, and freshly grated Parmigiano. Very tasty, and the seasoning will work equally well on stuffed pasta (with cheese and vegetable fillings) or flat pasta.
You could also make a somewhat thicker walnut oil and zucchini sauce:
Set your pasta water to boil, and while it's heating steam a half pound (225 g) baby zucchini.
When they're fork-tender trim the tips and puree them in a blender with 6-8 fresh basil leaves; by now the pasta water should be boiling, and you should cook the pasta (figure a scant pound, 400 g to serve 4). While it's cooking add to the pureed zucchini 8 tablespoons of walnut oil, freshly grated Parmigiano to taste, and check seasoning.
When the pasta is done, drain it, season it with the sauce, and serve at once with a white wine, for example, an Erbaluce from northern Piemonte.
Another Salad Idea
As noted above, walnut oil is wonderful with salad.
Greens, of course, but it is also nice in this winter salad made with cooked vegetables:
2 onions, either roasted in the oven or wrapped in foil and baked in the coals
2 beets, baked or boiled
Salt and pepper
A sprinkling of vinegar
A garlic clove, crushed or finely sliced (depending on how much you like garlic)
Peel and quarter the onions, or cut them into smaller pieces if they're large. Peel and slice the beets. Combine the vegetables in a salad bowl with the garlic.
Season to taste with walnut oil, salt, pepper, and vinegar, and mix well. Let the salad sit, covered, for at least a half hour in a cool but not too cold place.
Come time to serve the salad, remove the garlic (if you want) and mix the salad well.
Finally, you can use walnut oil to season meats, for example, rare veal. To serve 8-10, you'll need:
2 1/4 pounds (1 k) lean tender veal, for example, loin or round, tied with butcher's twine, so it keeps its shape
Meat or vegetable broth sufficient to cover the meat, about 1 quart (1 liter)
Salt and pepper
Fruit Mostarda, ideally apple (optional)
Heat the broth in a pot, and when it comes to a boil immerse the meat.
Let it come back to a boil, and simmer the meat for 15 minutes more; when it is done it should be springy to the touch, and the juices should run clear if you stick it. Turn off the heat, let the pot cool, and chill it and the meat for several hours in the refrigerator.
Come time to serve it, whisk several tablespoons of walnut oil with lemon juice, salt, and pepper to taste, or with a tablespoon of mostarda. Finely slice the meat, spoon the sauce over it, and serve at once, again with Erbaluce.
Looking further afield, walnut oil will be a nice addition to dishes like chicken or egg salad, and will also be nice sprinkled into stir-fried vegetables after you have removed the wok from the burner.