IN A 1-QUART SAUCEPAN over high heat, combine the garlic, capers, white wine and lemon juice and cook, reducing by one-third. Add the cream, reduce the heat to medium and continue to cook until the liquid starts to thicken, another 3 minutes. Remove from heat and whisk in 2 tablespoons butter. Set the sauce aside in a warm place. Pat the whitefish (or shad) dry on towels. Dust with flour, shaking off the excess. Heat the oil and remaining butter in a skillet over medium heat and add the fish. Saute until golden, about 6 minutes per side. Arrange the fish on a heated platter and top with the reserved sauce.