Preheat a deep-fryer to 375℉ (190℃) and pour vegetable oil in halfway full. Or heat the oil in a large saucepan.
Mix cornmeal, flour, garlic and onion powder, cayenne, salt, and pepper in a large bowl.
Mix buttermilk and eggs. Set aside.
Dip shrimp in the buttermilk mixture, then lightly roll in the flour mixture.
Then, fry the shrimp in the fryer or saucepan a few at a time until slightly golden and crispy, 3-4 minutes, depending on the size. These big guys took about 6 minutes.
Remove from the fryer with a slotted spoon and drain on a plate with a paper towel to ensure crispness. Repeat with the remaining shrimp.
Make the remoulade in a serving bowl by combining the freshly squeezed lemon juice, mayonnaise, garlic, relish, green onions, mustard, hot sauce, Worcestershire sauce, Creole seasoning, salt, and pepper.
Toast bread lightly in the oven.
While the bread is toasting, combine the crushed garlic and butter. Then melt it in a microwave-safe bowl for about 1 minute in the microwave.
Remove and spread it on the toasted bread.
Assemble the sandwich by adding the shrimp, sliced cabbage or shredded lettuce, sliced tomatoes, and drizzle with remoulade sauce.