- Trim root ends of lettuce heads and separate all leaves. Wash leaves in very cold water and dry well.
- Using Japanese mandoline, shave fennel and radishes paper-thin. Refrigerate lettuce with shaved fennel and radish until needed.
- Preheat tabletop fryer to 350 degrees. Dust oysters in flour and deep fry 1 minute. Drain fried oysters on paper towel-lined tray and season with salt and pepper.
- Toss lettuce, fennel, and radishes in large mixing bowl with olive oil and salt and pepper to taste. Spoon 2 tablespoons of Buttermilk Ravigote into 4 large bowls. Divide lettuce and vegetables into 4 equal portions and place on top of Ravigote. Top each lettuce mound with 6 fried oysters. Garnish with 6 slices Pickled Onions and fennel fronds.
- Place onion slices in pint jar. Heat remaining ingredients in medium saucepan over medium heat until sugar dissolves and pour over onions. Let cool to room temperature then refrigerate until needed.
- Whisk together all ingredients and refrigerate until needed.