Steam the cauliflower. Put cut cauliflower into a microwave safe-bowl with 1 cup of plain water. Cover with a moist paper-towel & microwave on high for about 3 mins or until the cauliflower is tender. Do not overcook!
Drain the cauliflower pat dry using a paper-towel. Put aside.
Preheat oven to 400°F.
In a skillet over medium-high heat cook the Italian-sausage, roughly 15 mins. After the sausage has completed cooking drain the excess fat. Put aside.
At precisely the exact same skillet olive-oil & saute mushrooms over medium-heat for 10 mins to remove the excess water. Set aside when done.
Get a 13×9 inch casserole dish by spraying it by non-stick spray subsequently disperse 1/2 cup of pasta-sauce at the ground.
In a large-bowl add the cauliflower, cooked Italian-sausage, mushrooms & green-pepper. Toss together till well blended.
Spread 1/2 of this mixture from the casserole-dish. Best using 1/2 cup of pasta-sauce, then followed closely by 1/2 of this pepperonis (type of press down them between another toppings), and 6 oz of mozzarella-cheese.
Next disperse the remaining batter mixture on the cheese followed closely from the pepperonis (store 10 pieces for the surface of the casserole), staying 1/2 cup of pasta-sauce, along with 6 oz of mozzarella-cheese.
In a small-bowl blend together the Parmesan-cheese and Italian-seasoning.
Sprinkle the Parmesan mixture over the casserole and top with 10 pieces of pepperoni.
Put in oven and bake for half an hour, or until the casserole is heated throughout and the cheese is completely melted.