Butternut Squash Risotto With Mushrooms

Name: Butternut Squash Risotto With Mushrooms
Ingredients: 1 pound butternut squash, peels and seeds removed, roughly chunked; 1/4 cup olive oil; 1 pound mixed wild mushrooms, especially oyster, shiitake, and chanterelles; 1 pinch salt and pepper, plus more to taste; 4 shallots; 4 cloves garlic; 2 stalks celery; 4 tablespoons unsalted butter; 4 fresh bay leaves; 1/2 teaspoon dried thyme; 2 cups arborio rice; 1/2 cup white wine; 6 to 8 cups chicken stock, heated; 1/2 cup heavy cream; 1 egg yolk; 1/2 cup freshly grated Pecorino Romano, plus more to taste