Preparation

Preheat oven to 400°F. Coat a 3-½ quart oval or rectangular baker with 1 tablespoon of the butter and reserve.Insert metal “s” blade in the work bowl. Place bread cubes in work bowl and process until they are coarse crumbs, about 30 to 40 seconds. Add remaining butter and ½ cup of the Parmigiano-Reggiano to the work bowl. Process until crumbs are somewhat fine, about 30 to 40 seconds longer. Remove and reserve.With machine running, drop garlic through small feed tube and process to chop, 10 seconds. Add cornstarch, salt, and pepper. With machine running, add half-and-half through small feed tube and process to blend, 15 seconds. Transfer to a 3-quart saucepan and stir in milk and herbes de Provence. Cook over medium heat, stirring constantly, until mixture begins to thicken, about 8 to 10 minutes. Stir in remaining cheese and reserve.Insert the medium (4-mm) slicing disc. Cut a flat edge on each potato. Arrange potatoes, flat edge down in the large feed tube. Use medium pressure to slice potatoes – this will be done in several batches. Remove and reserve. Arrange fennel bulbs in large feed tube, use medium pressure to slice. Remove and reserve.Using one third of the potatoes, arrange and overlap the potatoes in a layer, in the prepared baking dish. Using half the fennel, arrange in a layer over the potatoes. Pour one third of the warm milk/cheese mixture over the layers. Repeat the layers using half the remaining potatoes for the next layer, all the remaining fennel for the next layer, and the remaining potatoes for the top layer. Pour the remaining milk/cheese mixture over top, pressing down on the potatoes to submerge. Top evenly with the reserved crumb mixture. Lightly coat a large piece of aluminum foil with cooking spray. Cover baking dish with foil, coated side down. Place in oven and bake covered for 1½ to 1¾ hours. Remove foil and bake for an additional 30 minutes. Let stand 10 minutes before serving.