This step is very important in order to saute the fillets properly.
Place a large piece of waxed paper on your work surface and measure the flour onto it.
Sprinkle with the pepper, then spread the flour out.
In a large skillet, melt the butter with the oil over medium heat.
Meanwhile, lightly dredge the fillets in the flour.
Dredging must be done at the last minute to assure a crisp coating.
When the butter foam has subsided, slip the fillets into the skillet.
Saute over medium to medium-high heat until lightly golden, about 1 minute on each side depending on the thickness of the fillets, turning them only once.
Transfer to a heated platter and reduce the heat to medium-low.
Add the capers and wine.
Stir to scrape up any browned bits from the bottom of the pan.
Cook until the alcohol has evaporated, about 2 minutes.
Stir in the parsley and salt.
Remove the pan from the heat and pour the sauce over the fish.