How to Make It
In a medium saucepan, add the fish stock and garlic cloves, and bring to a simmer over medium. Reduce the temperature to low, and cook 30 minutes. Remove from heat, and add the cream and sage leaves; let stand 15 minutes. Remove and discard the sage leaves. Transfer stock mixture to a blender, and puree until smooth. Season with salt and white pepper, and set aside.
Stuff the fish with lemon slices and, if desired, thyme, rosemary, mint, and lime leaves. (Any variety of fresh herbs can be used.) Score the fish on each side and place in a fish grilling basket. Season with salt and white pepper. Brush fish with oil, and grill on 1 side until charred, about 6 minutes. Turn and grill until charred on second side and cooked through, about 6 minutes. Serve hot with the garlic sauce.