Low-Carb Turkey Casserole

Name: Low-Carb Turkey Casserole
Prep time: 45 min
Cook time: 40 min
Total time: 1 h 25 min
Cuisine: American
Ingredients: 6 cups chopped cauliflower (see notes); 1 pound Crimini mushrooms, washed and sliced; 4 cups cooked leftover turkey or chicken; 1 onion, chopped; 2 T olive oil, divided (more or less depending on your pan); 1 tsp. dried thyme; 1 tsp. dried Poultry Seasoning; salt and fresh-ground black pepper to taste; 1 cup coarsely grated Mozzarella (or more); 1 cup sour cream; 1/2 cup mayo; 2 T Dijon mustard; 1/2 tsp. dried thyme; 1/2 tsp. dried Poultry seasoning; 1 cup grated Mozzarella; 1/4 cup coarsely grated Parmesan cheese