Pulse the shrimp, egg, soy sauce, garlic powder and cayenne pepper sauce in a food processor just until everything is in small bits. Stir in tilapia. Form into 6 patties, 2/3 cup each, about 1/2 inch thick. Chill for 30 minutes.
Char the poblano peppers on all sides on 450 degrees grill until blackened. Place in a zip top bag and let sit for 20 minutes. Remove peppers and then wipe vigorously with a paper towel, until all charred skin is removed. Slice into 2 inch wide strips.
Blend in blender 2 avocados, 1/4 cup mayonnaise, lime juice, jalapeno, garlic cloves, 1 teaspoon salt and cayenne pepper sauce. Chill for at least 20 minutes.
Cut apple into very thin matchstick pieces.
Heat a grill on one side to 450 degrees. Spread 1 teaspoon of mayonnaise on one side of each of the shrimp patties. Cook patties on grill over indirect heat, mayonnaise side down, for about 3 minutes, until golden brown on bottom side. Spread one teaspoon of mayonnaise on uncooked side. Flip patties over, and cook for another 2 to 3 minutes, until golden brown on both sides. Remove from heat.
Brush buns with melted butter and place buttered side down on grill for a minute or two, until lightly toasted.
Assemble burgers as follows: 1 tablespoon avocado mixture on bottom bun, poblano strips to fit bun, shrimp patty, a little of the apple pieces, slices of tomato to fit bun, 1 tablespoon of avocado mixture on top bun, placed down on top.