Mushroom Gruyère Chicken & Rice Casserole Elegant yet easy, this creamy chicken and rice casserole with earthy mushrooms and melty Gruyère is comfort food with a gourmet twist—perfect for holiday gatherings or a cozy Christmas dinner side. Ingredients: 1 lb (450g) boneless, skinless chicken breasts or thighs, diced 1 tbsp olive oil 1 small onion, finely chopped 3 cloves garlic, minced 8 oz (225g) mushrooms, sliced (cremini or white) 1 cup long grain white rice (uncooked) 2 ¼ cups chicken broth 1