Beefy Cheesy Mexican Casserole Recipe

Name: Beefy Cheesy Mexican Casserole Recipe
Ingredients: 1 ½ tablespoons olive oil, for frying; 1 small onion, finely chopped; 1 red bell pepper, chopped; ½ teaspoon garlic powder; 1 teaspoon ground cumin; 1 teaspoon paprika; ½ teaspoon ground coriander; ½ teaspoon dried oregano; ½ teaspoon chili powder; 1lb lean beef mince; 1 can chopped tomatoes; 1 tablespoon tomato paste; 1 cup beef stock; ½ cup canned sweetcorn; ½ cup black beans; 12 small corn tortillas, cut into strips; 1 14oz can of refried beans; 2 cups grated cheddar cheese; 2 tablespoons fresh coriander, chopped; ½ cup sour cream, to serve; 1 avocado, sliced, to serve