Brown Butter Butternut Squash Pasta

Ingredients: 1 pound pasta (such as fettuccine, pappardelle, or your favorite shape) 4 tablespoons unsalted butter 1 small butternut squash, peeled, seeded, and cut into small cubes 2 cloves garlic, minced 1 teaspoon fresh thyme leaves (or 1/2 teaspoon dried thyme) Salt and freshly ground black pepper to taste 1/2 cup grated Parmesan cheese 1/4 cup chopped walnuts or pecans (optional) Fresh sage leaves (optional, for garnish)