Step 1 Slice chicken breasts into strips, and slice strips in half. Season with salt and pepper.
Step 2 Heat oil in medium skillet over high heat. Add chicken and sprinkle with chili powder, lime juice and garlic. Cook until chicken is no longer pink inside, stirring occasionally, about 5 minutes.
Step 3Divide tortillas between 2 baking sheets. Spread each tortilla with 1/4 cup beans, 1/4 cup sliced avocado, 1/4 cup tomatoes and 1/2 cup cheese. Broil until cheese is melted and bubbly, 1 to 3 minutes.
Step 4Pour 2 tablespoons taco sauce over melted cheese on each burrito. Divide chicken among tortillas. Top with 1 to 2 tablespoons sour cream. Roll up tortillas by folding bottoms up 1/4 of the way, then sides so that they overlap each other.