Heat butter in large skillet over medium-high heat and swirl so the skillet is generously coated. When foam subsides, add fish and cook until golden brown on both sides, about 6 minutes. When you turn the fish, you may need to use 2 spatulas. Sole is very delicate and can fall apart when you turn it. To avoid this make sure the bottom of the fish is golden brown before turning it over. Set cooked fish aside on a separate platter and cover loosely with foil. This will keep the fish warm while you make the sauce. Pour off drippings from skillet; wipe with paper towels.