Preheat oven to 350°F. Grease 9x13 inch baking dish.
In a large skillet, fry beef over medium heat until fully cooked and no longer pink. Drain (rinse if desired). Add beans, chilies, taco seasoning, and hot salsa and stir well.
Layer 4 noodles, ⅓ of the meat mixture, ⅓ of mushrooms, and 1 cup of cheese. Repeat layers, adding two more layers, ending with cheese. I had 5 noodles on my top layer of noodles.
Mix water with mild salsa and carefully pour over top of the cheese. Cover baking pan and bake 1 hour or until heated through.
Top with sour cream and remaining cheese. Bake, uncovered, 5 minutes. Let stand 10-15 minutes before cutting.
Garnish with sliced olives, green onions, and chopped tomatoes.
Notes
Nutrition calculated without optional toppings.
Refrigerate leftovers in a covered container for up to 3 days and reheat portions in the microwave.
Freeze portions in freezer-safe containers for up to 1 month.