Combine the mayonnaise, sour cream, dijon, whole grain mustard, ketchup, vinegar, tabasco, capers and scallion in a bowl. Whisk to combine. Taste for seasoning and add salt and pepper as needed. Set aside.
For The Oysters:
Set up a dredging station with 3 shallow bowls. The first bowl is flour, salt and pepper, mixed together to combine. 2nd bowl is whipped eggs & half and half. 3rd bowl is cornmeal.
Place several layers of paper towels on a baking sheet and set aside.
Heat oil in a fryer or dutch oven to 350-375°. Test oil by dropping a grain of rice into the oil. If it immediately comes to the surface and starts to cook, it's perfect.
Pat oysters lightly with a paper towel. Dip one oyster into the flour mixture to lightly coat, transfer to the eggs and coat, then dip in cornmeal. Transfer the oysters to the hot skillet, cooking no more than 3-4 at a time. Cook for 2-3 minutes, flipping halfway through. Transfer oysters to the prepared pan and continue with the rest of the batch.