Pre-heat oven to 390ºF/200ºC.
Mix the panko breadcrumbs with the taco seasoning.
Spray a baking sheet with a very generous layer of oil then spread the seasoned panko over the tray. Mix gently with your hands.
Bake for 5-7 minutes until golden.
Remove from the oven and increase the oven temperature to 430ºF/220ºC.
Break an egg into a shallow bowl and lightly whisk to mix the white and yolk. Add in the flour, mayonnaise, mustard, taco seasoning, and salt (if needed) then mix to form a thick paste.
Place the chicken smooth side up on a sheet of baking paper or gladwrap/clingfilm. Cover with a second sheet and use a rolling pin or smooth meat hammer to flatten the chicken until it is about ½ inch thick all over. Repeat with all 4 chicken breasts.
Set a wire rack over a baking sheet and spray/brush lightly with oil.
Dip the chicken breast into the batter then transfer to the tray of breadcrumbs. Carefully flip the chicken so both sides are well coated with the crispy crumb. Place onto the oiled rack and repeat with the remaining chicken breasts.
Bake the chicken for 10 minutes until crispy and golden.
Peel the avocado and remove the pit.
Use a fork to smash the avocado together with a little salt.
Once the chicken has cooked turn the broiler to high.
Top each chicken schnitzel with some smashed avocado. Sprinkle over the beans, bell pepper, tomato, red onion, and fresh cilantro. Top each schnitzel with ¼ cup of grated cheese.
Place under the broiler for 2-4 minutes until melted and golden.
Serve immediately.
