Heat 6 cups of boiling water in a large pot. Preheat oven to 375 degrees F.
Trim the fronds and base from the fennel bulbs and cut the fennel into 1 to 2-inch strips. Remove any woody centers.
Place the fennel bulbs in the boiling water and let simmer for 7 minutes.
Meanwhile, combine the Panko breadcrumbs, parmesan cheese, parsley, salt, and pepper in a small bowl.
Drain the fennel and place in a baking dish. Drizzle with the olive oil and melted butter, then mix half the breadcrumb mixture with the fennel and spread the rest across the top.
Bake, covered with tin foil, for 25 minutes. Remove the tin foil and bake an additional 20 minutes or until the top is browned.