Tomato Free Mexican Lasagna

Name: Tomato Free Mexican Lasagna
Ingredients: 8 smalls corn tortillas; 1 pound extra lean ground beef; 1 small onion, diced; 3 large garlic cloves, minced; 1 portobello mushrooms, minced; 4 ounces can diced green chilies [use diced jalapenos if desire more spicy]; 1 cup canned black beans, washed, drained; 1 cup canned corn, drained; 1/2 teaspoon oregano; 1/2 teaspoon chili powder; 1/4 teaspoon garlic powder; 1 1/4 teaspoons cumin; 1/2 teaspoon fresh ground black pepper; 1 teaspoon kosher salt; 1/2 cup plus ¾ c reduced fat shredded Mexican blend cheese; 1 cup shredded iceberg lettuce; avocado diced