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 upon 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 bucher'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.
More suggestions, and a couple of recipes, from The Epicentre
Il Museo Laboratorio del Mortigliengo: an interesting page dedicated to a traditional walnut oil press in Biella. In Italian, alas.