10 medium fennel bulbs—halved, cored and sliced 1/2 inch thick
1 cup extra-virgin olive oil
Kosher salt and freshly ground pepper
2 cups panko (Japanese bread crumbs)
1 cup finely grated Parmigiano-Reggiano cheese
2 tablespoons all-purpose flour
2 tablespoons unsalted butter
2 garlic cloves, minced
2 shallots, minced
2 teaspoons chopped thyme
2 tablespoons chopped flat-leaf parsley
1/4 cup dry white wine
Preheat the oven to 375°. On 2 large rimmed baking sheets, drizzle the fennel with 1/2 cup of the olive oil; season with salt and pepper. Bake for 45 minutes, until softened. Let cool for 30 minutes.
In a skillet, toast the panko over moderate heat until golden, 3 minutes. Transfer to a bowl; stir in the cheese and flour.
In the same skillet, melt the butter. Add the garlic, shallots and thyme and cook over moderate heat until the garlic is softened, 5 minutes; add to the panko. Stir in the remaining 1/2 cup of oil and the parsley. Season with salt and pepper.
Preheat the oven to 400°. Spread half of the fennel in a 9-by-13-inch glass or ceramic baking dish. Pour the wine over the fennel, then sprinkle half of the panko on top. Repeat with the remaining fennel and panko. Cover and bake for 20 minutes, then remove the foil and bake for 10 minutes longer, until the topping is browned and crisp. Serve hot.
The unbaked gratin can be wrapped in foil and frozen for up to a week. Bake the foil-wrapped dish straight from the freezer for 25 minutes, then remove the foil and bake for 15 minutes longer.