Pepperoni Pierogi Casserole

Ingredients
16 oz. frozen pierogis - you can use any flavor you prefer.  I typically use potato & cheddar.
1 (15 oz) can tomato sauce
1 (14.5 oz) can diced tomatoes
1/2 a large green pepper, diced
1/2 cup pepperoni, cut into small pieces
1 1/2 cups shredded mozzarella cheese

To assemble:
Place frozen pierogi in a baking dish in a single layer.  In a bowl, mix together tomato sauce, diced tomatoes, diced green pepper & pepperoni.  Pour mixture over frozen pierogi & top with cheese.  Cover baking dish with with foil & freeze.

To serve:
Thaw overnight, then bake 20 - 25 minutes at 350 degrees, or until cheese is melted & pierogi are heated through.

Adapted from a recipe I found on the side of a box of Mrs. T's pierogis years ago :)