Enchilada Casserole (my version)

Ingredients

• 2 pounds ground sirloin
• 1 onion chopped
• 2 (8-oz) cans tomato sauce
• 1 small can mushroom stems & pieces, drained
• 1 small can ripe olives, drained and coarsely chopped
• 1 pkg. taco seasoning mix
• 1 dozen corn tortillas
• 1 can cream of chicken soup
• 3/4 cup milk
• 2 cups grated Mexican blend cheese