Step 1

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.)

Step 2

Preheat oven to 375F/190C.

Step 3

Chop up enough cauliflower to make 6 cups of small cauliflower pieces. Then 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.)

Step 4

Use frozen cauliflower rice if you prefer, about 3 cups.

Step 5

Wash the mushrooms and cut into thick half slices.

Step 6

Dice the leftover turkey (or chicken) into bite-sized pieces.

Step 7

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.

Step 8

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.

Step 9

Put mushrooms in the bottom of the casserole dish.

Step 10

Add about 2 tsp. more olive oil and saute the onions over medium-high heat until they are softened and starting to brown.

Step 11

Put onions over the mushrooms in the casserole dish.

Step 12

Heat another 2 tsp. of olive oil and add the finely-chopped cauliflower.

Step 13

Cook over medium-high heat, stirring often, until the cauliflower is starting to soften and barely brown, about 3-4 minutes (or slightly less for frozen cauliflower rice).

Step 14

Add the 1 teaspoon each of dried thyme and Poultry Seasoning and cook about 1 minute more.

Step 15

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.

Step 16

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!)

Step 17

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.

Step 18

Wipe off the sides of the casserole dish with a paper towel if needed.

Step 19

Sprinkle with Mozzarella cheese and bake uncovered until the casserole is starting to bubble and the top is nicely browned, about 40 minutes.

Step 20

Let cool about 5 minutes; then cut into 8 servings and eat while hot.