Fennel Gratin with Parmesan Bread Crumbs

Name: Fennel Gratin with Parmesan Bread Crumbs
Prep time: 25 min
Total time: 25 min
Cuisine: European, Mediterranean, French
Ingredients: 5 medium fennel bulbs (about 2 1/2 lb), trimmed and cut into 1/2-inch wedges, fronds reserved (6 cups); 2 tablespoons butter, melted; 3 tablespoons butter; 2 cups thinly sliced onions; 1/2 teaspoon salt; 1/4 teaspoon crushed red pepper flakes; 4 tablespoons all-purpose flour; 1 cup Progresso™ chicken broth (from 32-oz carton); 1 cup heavy whipping cream; 1 cup Progresso™ plain panko crispy bread crumbs; 1 cup shredded Parmesan cheese (4 oz)