Radicchio is a gorgeous winter vegetable, its dappled maroon-red leaves decorating gardens, farm stands, and salad bowls. There are actually several varieties of this handsome winter crop. Round balls of radicchio di Chioggia, looking like small red cabbages, are easily found in North American supermarket produce sections where they’re considered salad “greens”—and delicious too with a crunch and edgy bitterness. Radicchio di Treviso (or radicchio di Verona), on the other hand, may take a little searching for. It has the same coloration, but its shape is long and slender, and, unlike its cousin, it is often cooked—painted with oil and roasted whole on the grill, or chopped and braised to serve with pasta, as in this recipe, or in a risotto. If you come across it, snap it up—its bitterness is a welcome clue to the health-giving antioxidants that lurk inside.
If you can’t find Treviso, could you do this with radicchio di Chioggia, the round kind? Yes, you could, but it does not have the refreshing bitterness of Treviso and, because it contains a good deal more water, it will take more time to caramelize successfully.
Keep in mind that the best ricotta is always the freshest, and even better if it’s made with whey from cheese making, either sheep or goat, but cow’s-milk ricotta will also do for this dish (see here for more on ricotta).
SERVES 4 TO 6
1 medium onion, diced
¼ cup extra-virgin olive oil
1 cup walnut halves
4 cups coarsely chopped or sliced radicchio di Treviso
1 cup real ricotta
Sea salt and freshly ground black pepper
About 1 pound (500 grams) fusilli or other short, complex pasta shape
Combine the onion with the oil in a deep skillet large enough to hold all the sauce ingredients and set over low heat. Give the onion an occasional stir, but otherwise just let it cook gently while you prepare the rest of the sauce—the onion should melt in the oil but not brown.
Set the oven on 300ºF.
While the onion is cooking, spread the walnut halves on a cookie sheet and toast for several minutes, until the nuts begin to release their odor. It’s okay if they turn a little golden, but don’t let them get deep brown.
When the onion slices are done, stir in the chopped radicchio, cover the pan, and return to the heat, raising it slightly to medium-low to cook. Check from time to time—if the radicchio doesn’t release enough liquid, add a couple of tablespoons of hot water to the pan. When the radicchio is thoroughly wilted, uncover the pan and raise the heat again, this time to medium, cooking vigorously to caramelize slightly.
Chop the walnuts coarsely. Set aside a couple of tablespoons to use as a garnish and stir the rest of the walnuts into the radicchio. Add salt and plenty of pepper and keep the sauce warm while you cook the pasta.
Bring a large pot of water to a rolling boil. Add salt and the pasta and cook following the package directions, until al dente. Just before draining the pasta, add a ladleful of pasta water to the radicchio sauce and return the sauce to a very low simmer. Remove the pan from the heat and stir in the ricotta.
Drain the pasta, transfer immediately to a warm bowl, add the sauce, and toss to mix thoroughly. Garnish with the reserved walnuts and serve immediately.
VARIATION If you wish, pass a bowl of freshly grated parmigiano-reggiano to add to the pasta at the table.