Place ingredients in mixing bowl and whisk until well combined. Transfer to storage container, cover, and refrigerate for up to one week.
For the Oysters
In a mixing bowl, combine the flour with salt and pepper .
Remove oysters from liquor, draining excess so oysters are still wet but not dripping.
One at a time, toss the oysters to coat all sides in the breading (gently press the breading onto the oyster to help it adhere). Transfer to waxed-paper-lined plate or cookie sheet until oysters are all breaded.
In a heavy stockpot with high sides fitted with a deep-frying (or candy) thermometer, bring at least two inches of peanut oil to 375ºF.
Keeping the heat at a steady 375ºF and working in batches of six, fry the oysters until they are golden brown and just cooked through, about 90 seconds. (The oysters will curl slightly when they are done.) Using a slotted spoon, remove oysters and drain on brown-paper-bag-lined plate.
to build the po’boy
Heat a large skillet or griddle. Slit the hoagie buns and butter the insides. Place on a griddle and toast until golden and browning on the side. Flip and cook just a few seconds just to warm.
Slather both sides with the rémoulade.
Pile some shredded lettuce on the bottom bun, then pile with the fried oysters. Top with the sliced tomatoes that have been lightly salt and peppered. Slice in half and enjoy!