In a mixing bowl, combine the shrimp, onion, water chestnuts, celery, and green onion. Stir in crabmeat, egg, parsley, sesame oil, soy sauce, and garlic. Season with salt and pepper to taste.
Make the dipping sauce: In a small mixing bowl, whisk together soy sauce, water, sesame oil, parsley, garlic powder, and sugar; set aside.
In a heavy skillet, heat 2 cups oil, or enough to be 1/2 inch deep, over medium heat. Spread a thick layer of shrimp filling on one side of each slice of bread.
Fry the topped bread in hot oil until golden brown and shrimp is pink, turning once. Do not let the filling sit on the bread too long or the sandwich will get soggy. Drain on paper towels and let cool for a minute. Slice diagonally and serve with dipping sauce or alone.
