Red Snapper with Mediterranean Ragout

INGREDIENTS

• 2/3 cup white wine
• 3 pounds red snapper, cut into 6 pieces, skin on and scored
• Kosher salt and freshly ground black pepper
• 1/4 cup olive oil
• 1 tablespoon chopped fresh rosemary
• 20 cloves roasted garlic, see Cook's Note*
• 12 cherry tomatoes, halved
• 2 tablespoons chopped fresh Italian parsley leaves
• 2 tablespoons chopped fresh thyme
• 2 cups fish stock, recipe follows
• 12 black olives, pitted
• 1 tablespoon olive oil
• Special equipment: a rectangular casserole dish
• 1 pound Yukon gold potatoes, cut into 1/8-inch thick slices
• 2 cups onions, thinly sliced