Season both sides of the fillets with 1 teaspoon of the salt and the white pepper. Lay 2 slices of the prosciutto side by side on a piece of plastic wrap. Put 1 fillet skin side down on top of the prosciutto and wrap the fish in it, folding the prosciutto tightly around the sides to completely enclose the fish. Repeat the procedure with the remaining prosciutto and fish.
Heat 2 tablespoons of the oil in a large heavy skillet over medium-high heat until it begins to smoke. Place the fillets skin side down in the pan and cook until the prosciutto is golden brown and the fillets are opaque throughout, about 3 minutes on each side. Transfer the fish to a platter and tent with aluminum foil to keep warm.
Add the remaining 1 tablespoon oil to the skillet. Add the shallots and garlic and cook, stirring, until fragrant, about 30 seconds. Add the tomatoes and capers and cook, stirring often, until the tomatoes are heated through, about 3 minutes. Add the white wine and increase the heat to high. Boil until the liquid is reduced by two-thirds, about 2 minutes. Add the cream and reduce by half, about 2 minutes.
Remove the pan from the heat. One cube at a time, whisk in the butter until it makes a smooth sauce. Add the parsley, the 1/2 teaspoon remaining salt, and the black pepper. Transfer to a sauceboat or bowl.
Serve the fish with the sauce passed on the side.
Yield: 4 servings