Thanks to Epicurious for another amazing recipe!
3 TBSP butter
3/4 c panko
1 c Pecorino, grated
1 TBSP chopped fresh Italian parsley
1 1/2 tsp finely grated lemon peel
2 TBSP olive oil
1 onion, halved, cut into 1/4-inch-thick slices
3 large garlic cloves, minced
5 fennel bulbs, trimmed, cored, cut into 1/4-inch-thick slices
1/2 c low-salt chicken broth
2 TBSP chopped fresh Italian parsley
1 TBSP chopped fresh thyme
1 1/2 tsp salt
1/2 tsp black pepper
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.
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.
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.