This recipe brings together sweet halibut, the salty twang of anchovies, tart lemon juice and the beguiling flavor of capers.
Heat oven to 400 degrees. Put a large skillet, preferably nonstick, over medium-high heat, and leave it there until hot. Add oil and butter together. Butter should sizzle. When butter foam subsides, add fish, and season it lightly with salt and pepper. Brown fish, basting with pan juices, then turn, and brown again. Do not worry about cooking through. Turn off heat, put fish on an ovenproof plate, and place it in oven.
Turn heat under skillet to medium, and add anchovies and garlic. Cook, stirring occasionally, until anchovies break up, just a couple of minutes. Add capers and wine, and turn heat to high. Cook until wine is reduced by half. Return fish and its juices to pan, and turn it in sauce once or twice. Fish should be cooked through by now. (A thin-bladed knife inserted into its thickest part will meet little resistance.)
Taste sauce, add some lemon juice, then taste again. It should be strong-tasting but only mildly acidic. Remove fish to serving plate, spoon sauce on top, and garnish with parsley.