You can also use chicken to make this Low-Carb and Gluten-Free Turkey Casserole with Mushrooms, Mozzarella, and Cauliflower Rice.
(Makes 8 servings; recipe created by Kalyn and Kara, after many previous attempts that were not keepers!)
6 cups chopped cauliflower
1 pound Crimini (Baby Bella) 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; I used reduced-fat Mozzarella)
1 cup sour cream (regular or light but do not use fat-free which has added sugar)
1/2 cup mayo
2 T Dijon mustard
1/2 tsp. dried thyme
1/2 tsp. dried Poultry seasoning
1 cup grated Mozzarella (I used reduced-fat Mozzarella)
1/4 cup coarsely grated Parmesan cheese
Spray a large glass or crockery casserole dish with olive oil or non-stick spray. (I used a dish that was 10" x 13" but any size that's close to that will work.) Preheat oven to 375F/190C.
Chop up enough cauliflower to make 6 cups of small cauliflower pieces. The use a food processor with a steel blade to pulse the cauliflower until it's finely chopped, slightly larger then kernels of rice. (See the recipe for cauliflower rice for more about how to do this. You can also chop the cauliflower by grating it on the side of a box grater.)
Wash the mushrooms and cut into thick half slices. Dice the leftover turkey (or chicken) into bite-sized pieces. Mix together the sour cream, mayo, Dijon mustard, 1/2 tsp each dried thyme and Poultry seasoning, 1 cup grated Mozzarella, and 1/4 cup Parmesan to make the thick sauce mixture.
Heat 2 tsp. olive oil in a large non-stick frying pan and saute the mushrooms over medium-high heat until they release their liquid, all liquid evaporates, and mushrooms are starting to brown. Put mushrooms in the bottom of the casserole dish. Add about 2 tsp. more olive oil and saute the onions over medium-high heat until they are softened and starting to brown. Put onions over the mushrooms in the casserole dish. Heat another 2 tsp. of olive oil and add the finely-chopped cauliflower. Cook over medium-high heat, stirring often, until the cauliflower is starting to soften and barely brown, about 3-4 minutes. Add the 1 teaspoon each of dried thyme and Poultry Seasoning and cook about 1 minute more. Season the cauliflower rice with a little salt and fresh-ground black pepper; then put it into the casserole dish over the mushrooms and onions.
Put the diced turkey into the casserole dish over the veggies and use a plastic spoon to combine the ingredients right in the dish. (You can do this in a bowl if you prefer, but we were trying to get away without dirtying another dish!) Spread the sauce mixture over the top and then use the spoon to gently combine the ingredients with the sauce, until the ingredients are well mixed into the sauce. Wipe off the sides of the casserole dish with a paper towel if needed. Sprinkle with Mozzarella cheese and bake uncovered until the casserole is starting to bubble and the top is nicely browned, about 40 minutes.
Let cool about 5 minutes; then cut into 8 servings and eat while hot. This kept amazingly well in the fridge for days, and can easily be reheated in the microwave or in a pan on top of the stove. I'm guessing it freezes well, but I ate all my leftovers before I could freeze any.