Pumpkin Risotto with Gorgonzola and Walnuts

Name: Pumpkin Risotto with Gorgonzola and Walnuts
Ingredients: 1 small (1¾ pound) pumpkin, peeled, seeded, and cut into 1-inch cubes; 4 Tablespoons extra-virgin olive oil; 1 medium white onion, diced; 2 cloves garlic, minced; 2 Cups Arborio rice; 1 Cup dry white wine; 4-6 Cups low-sodium chicken stock, as needed; 2 Tablespoons gorgonzola; 2 Tablespoons Parmigiano-Reggiano; 1 Teaspoon fresh sage, chopped; 2 Tablespoons unsalted butter; Kosher salt and freshly ground black pepper; Toasted walnuts