It seems to me that mushrooms must mean to vegetarians what steak means to carnivores. They are both stick-to-your-ribs, center-of-the-plate comfort foods. These days our supermarkets always boast a huge selection of mushrooms, many of which were terribly exotic a generation ago. My advice for this hearty vegetarian entree is to mix together a few of the exotics and add some button mushrooms for filler. But don’t combine too many of the most pronounced in flavor—such as morel and shiitake—because they will cancel each other out.
The real secret ingredient here, to be added at the last minute, is truffle oil. Truffle oil is like vanilla extract or Asian sesame oil, a little goes a long way. For a while in the nineties, chefs were putting it in everything, and it quickly became a cliché. But I still think a little truffle oil, used judiciously, can bestow on many dishes a final luxurious pick-me-up. It is one of those secret ingredients that make you look like a genius.
The mushroom ragout is served here on grilled polenta but it would be delicious tossed with fettuccini, too. Or make it part of an elegant first course by serving it on top of slices of grilled country bread rubbed with a raw garlic clove.
For the polenta:
1 quart while milk
1 teaspoon salt
1 cup polenta or yellow cornmeal
1/4 cup freshly grated Parmigiano-Reggiano
For the ragout:
3 tablespoons extra virgin olive oil
2 shallots, minced
2 garlic cloves, minced
1 pound cultivated white mushrooms, cleaned and finely chopped
1 pound assorted wild mushrooms, cleaned and coarsely chopped
2 to 3 plum tomatoes
1/2 cup dry white wine
1/2 cup vegetable stock, preferably homemade, or water
2 teaspoons chopped fresh thyme
Kosher salt and freshly ground black pepper to taste
Truffle oil to taste
2 tablespoons chopped fresh parsley
Additional grated Parmigiano-Reggiano for serving
To make the polenta, bring the milk with the salt to a boil in a large saucepan over high heat. Gradually add half the polenta, whisking constantly. Reduce the heat to medium low and add the remaining polenta in a slow, steady stream, whisking constantly. Reduce the heat to low and cook, whisking often, for about 20 minutes. Remove from the heat and stir in the cheese. Pour into an 8-inch square baking pan lined with oiled aluminum foil and smooth the top. Cool slightly, then cover with plastic wrap. Refrigerate until very well chilled, at least 6 hours or overnight.
Meanwhile, prepare the ragout. Heat the olive oil in a medium saucepan over medium high heat. Add the shallots and cook, stirring constantly, until slightly softened, about 2 minutes. Stir in the garlic and cook for 1 minute longer. Add all the mushrooms and cook, stirring, often, until the liquid they give off begins to evaporate, about 10 minutes. Add the tomatoes and the wine, increase the heat to high and bring to a boil. Stir until the liquid has evaporated. Reduce the heat to low and pour in the vegetable stock. Add the thyme and season with salt and pepper. You should have about 2 1/2 cups.
Just before serving, light a charcoal fire and let the coals burn down to a gray ash. Oil the grates and set the grill about 5 inches from the heat. (Alternatively, place a stovetop grill over medium-high heat.) Turn the polenta out of the pan onto a large work surface. Cut into 4 equal squares. Then cut each square in half diagonally to form triangles. Grill the triangles until heated through, 5 to 7 minutes per side.
Reheat the ragout and correct the seasoning with salt and pepper. Overlap 2 triangles on each of 4 serving plates (or serve 1 triangle per person as an appetizer.) Ladle on equal amounts of the ragout, drizzle with truffle oil, and sprinkle with parsley and cheese to taste. Serve hot.