Step 1

Preheat oven to 375F/190C. Spray a large glass or ceramic casserole dish with non-stick spray or brush with a little olive oil. (I used an oval-shaped dish that's 13 inches long and 10 inches wide at the widest part.)

Step 2

Mix the Better Than Bouillon Beef Base (or a bouillon cube) with 1/4 cup water; then simmer the mixture on the stove in a very small pan until it's reduced to 1 tablespoon thick stock. Let it cool.

Step 3

Heat a couple of teaspoons olive oil in a large heavy frying pan and cook the beef over medium-high heat until it's completely browned, breaking apart with the turner as it cooks. Put browned beef in the casserole dish.

Step 4

While beef browns, wash mushrooms and spin dry in a salad spinner, or let them drain well.

Step 5

Chop up the cauliflower and pulse in the food processor to make cauliflower rice if you're not using packed cauliflower rice.

Step 6

Cut drained mushrooms into quarters (or halves if they're small.) Heat a couple more teaspoons olive oil in the frying pan and cook mushrooms over medium high heat until they have lost all their liquid and are slightly browned. Put mushrooms in the casserole dish.

Step 7

Mix the sour cream and mayo and add the cooled and reduced stock and stir together.

Step 8

While mushrooms cook, chop an onion into small pieces. Heat two more teaspoons oil in the frying pan (if needed), add the onions, and cook over medium-high heat until onions are softened and starting to brown.

Step 9

Add the cauliflower rice, 1 tsp. steak seasoning, salt, and pepper to the frying pan with the onions. Turn heat to high and cook about 3 minutes, or until cauliflower is partly cooked and some liquid from the cauliflower has evaporated as steam.

Step 10

Add the onion-cauliflower rice mixture to the casserole dish and gently combine all the ingredients.

Step 11

Mix the 1 cup grated Mozzarella, Parmesan, and 1/2 tsp. steak seasoning into the mayo-sour cream mixture.

Step 12

Gently mix the sauce into the cauliflower rice-ground beef mixture in the casserole dish, patting it down when all the ingredients are well combined. Wipe off the edge of the casserole dish if it's messy.

Step 13

Top the casserole with 1 cup (or more) grated Mozzarella.

Step 14

Bake casserole 30-40 minutes, or until it's bubbling hot and the top is lightly browned.

Step 15

Serve hot. Leftovers of this will keep in the fridge for at least a week. It can be reheated in a microwave or in a small pan on the stove.