Combine the creme fraiche, 1/4 teaspoon of the salt, and 1/2 teaspoon of the pepper in a small bowl, and mix well. Transfer to a fine mesh strainer and place over a bowl. Let the mixture drain, refrigerated, for up to 2 hours. Cover until needed.
Drain the oysters in a fine mesh strainer over a bowl, and reserve their liquid to equal 1 1/2 cups.
Melt the butter in a medium pot over medium-high heat. Add the shallots and cook, stirring, for 2 minutes. Add cayenne pepper. Add the heavy cream, the 1 1/2 cups oyster liquor, and the liqueur, and bring to a boil over medium-high heat. Add the remaining 1 teaspoon of salt and 1 teaspoon of black pepper, and reduce the heat to medium. Simmer until reduced by 50 percent in volume, about 10 minutes. Remove from the heat. Add half of the spinach to the cream and puree with an immersion blender, or in batches in a blender or food processor. Strain through a fine-mesh strainer into a large clean saute pan, and keep warm.
Heat the oil in a medium stockpot to 350 degrees F.
Add the remaining spinach to the pot in batches and fry until crispy, about 45 seconds. With a slotted spoon remove the cooked spinach and drain on paper towels. Season lightly with salt to taste.
Add the oysters to the sauce and bring to a gentle simmer. Cook until the edges of the oysters start to curl, about 3 minutes, depending upon their size. Remove from the heat.
To serve, arrange 6 oysters around the inner edge of a shallow, rimmed soup bowl like the spokes of a wheel, and spoon 1/2 cup of sauce around the oysters.
Spoon a dollop of Black Pepper Creme Fraiche into the center of the bowl, top with a teaspoon of the Beluga caviar, and garnish with fried spinach. Repeat with the remaining ingredients and serve.