Beat the egg in a small bowl. In a shallow Tupperware container or large plate, combine the beaten egg with ~2 tablespoon of water to make a simple egg wash.
On another large plate, combine the breadcrumbs, parmesan cheese and salt and pepper.
One filet at a time, dip fish fillets in egg wash and then in bread crumb mixture to coat all over.
Heat 1-2 tablespoon vegetable oil in a non stick pan on medium heat.
Add fish to hot pan and let brown on each side (about 6-8 minutes each side). Fish should be opaque white in the centre. If using thicker pieces of fish, cover pan with a lid and let cook longer to cook through. Remove fish from pan.
Place one tortilla in the heated non-stick pan and turn down heat a bit to low-medium.
Spread layer of fish, shredded cheese, tomatoes, green onions, and peppers on one-half of the tortilla.
Fold the tortilla over and cook for a few minutes on low-medium heat.
Heat for a few more minutes. Check if cheese has melted by carefully lifting one side of the tortilla. Once cheese is melted and tortillas are toasted, slide onto a platter and cut into triangles.
Serve with lime wedges, smashed avocado, cilantro and salsa or chipotle sauce.