Ingredients

• 3 tablespoons butter
• 3/4 cup panko (Japanese breadcrumbs)
• 1 cup Pecorino Romano cheese
• 1 tablespoon chopped fresh Italian parsley
• 1 1/2 teaspoons finely grated lemon peel
• 5 tablespoons olive oil
• 1 12- to 13-ounce onion, halved, cut into 1/4-inch-thick slices
• 3 large garlic cloves, minced
• 5 large fresh fennel bulbs, trimmed, cored, cut into 1/4-inch-thick slices
• 1/2 cup low-salt chicken broth
• 2 tablespoons chopped fresh Italian parsley
• 1 tablespoon chopped fresh thyme
• 1 1/2 teaspoons coarse kosher salt
• 1/2 teaspoon black pepper
• Ingredient Info: Panko can be found in the Asian foods section of most supermarkets.

Instructions

1. Lightly oil shallow 2-quart glass or ceramic baking dish. Heat 5 tablespoons oil in large wide pot over medium heat. Add onion and garlic; sauté until soft but not brown, about 5 minutes. Add fennel; increase heat to medium-high and sautéuntil fennel is slightly softened and beginning to brown, stirring frequently, about 18 minutes. Stir in broth and next 4 ingredients. Reduce heat to medium-low; simmer until most of broth is absorbed, about 5 minutes. Transfer to dish.DO AHEAD: Can be made 1 day ahead. Cool slightly; cover and chill. Let stand at room temperature 1 hour before baking.
2. Crumb topping: Melt butter in large nonstick skillet over medium heat. Add panko; sauté until golden, about 3 minutes. Remove from heat; cool to room temperature. Stir Pecorino, parsley, and peel into panko. DO AHEAD: Can be made 1 day ahead. Store airtight in refrigerator. Preheat oven to 425°F. Sprinkle panko mixture over fennel. Bake until gratin is heated through and topping is deep golden, about 20 minutes. Serve warm.
3. Melt butter in large nonstick skillet over medium heat. Add panko; sauté until golden, about 3 minutes. Remove from heat; cool to room temperature. Stir Pecorino, parsley, and peel into panko. DO AHEAD: Can be made 1 day ahead. Store airtight in refrigerator.
4. Preheat oven to 425°F. Sprinkle panko mixture over fennel. Bake until gratin is heated through and topping is deep golden, about 20 minutes. Serve warm.