INGREDIENTS
Fennel
4 or 5 large fennel bulbs (each 3 to 4 inches), or 6 to 8 small fennel bulbs (each 2 to 3 inches), with some fronds attached
1 tablespoon salt
1 teaspoon freshly ground black pepper
2 tablespoons extra-virgin olive oil
4 tablespoons butter
¾ cup homemade stock or other high-quality stock
¼ cup good white wine
Cheese Sauce
3 tablespoons butter
3 tablespoons all-purpose flour
2 teaspoons garlic paste
2 ½ cups whole milk
3 ounces cave-aged Gruyère cheese, grated
½ teaspoon salt
¼ teaspoon freshly ground black pepper
Bread Crumb Topping
2 tablespoons butter
1 teaspoon garlic paste
½ teaspoon fennel pollen
¼ teaspoon freshly ground black pepper
3 tablespoons roughly chopped fennel fronds (optional)
For Assembly
2 ounces cave-aged Gruyère cheese, grated
2 ounces Parmigiano-Reggiano cheese, ground
DIRECTIONS
Make the fennel
Chop 3 tablespoons fennel fronds and set them aside for later use. If you’re using large fennel bulbs, cut them lengthwise into quarters; if you’re using small bulbs, cut lengthwise in half. Leave the base fully attached in both instances. Turn the fennel pieces cut side up and season with salt and pepper.
Heat your largest sauté pan over medium-high heat. Add oil and butter, and then working in batches to avoid overcrowding, add the fennel cut side down and sear until deep chestnut brown, 2 to 3 minutes. If fennel is quartered, flip pieces to sear the other cut surface for 2 to 3 minutes more. Transfer the fennel to a large Dutch oven.
Add the stock and wine to the Dutch oven, place over low heat, cover and simmer until fennel is fork-tender but not mushy, 20 to 25 minutes. If there is any liquid remaining in the pot, drain it off. Place the fennel in a 9 by 13-inch baking dish and set aside.
Make the cheese sauce
In a saucepan over medium heat, melt butter and whisk in flour. Whisk for about 1 minute, then add the garlic paste. Whisk until the flour begins to take on a pale gold color, 2 to 3 minutes. At this point, you will have removed any raw flour taste from your sauce. You don't want too much color, however, as the flour will taste bitter if it gets overly toasted. You want a shade between off-white and not quite beige when you stop whisking.
Gradually whisk in the milk to avoid forming any lumps. Once all of the milk has been added, whisk vigorously until sauce is completely smooth; turn down heat to medium-low and simmer, whisking periodically to avoid scorching, until sauce fully thickens, 10 to 12 minutes. Turn off heat, whisk in Gruyère, and season with salt and pepper. The finished sauce should be very thick.
Make the bread crumb topping
In a saucepan over medium-low heat, melt the butter. Add the bread crumbs, garlic paste, fennel pollen, and pepper and cook, stirring often, until the bread crumbs are pale gold. Don't allow them to take on too much color, as they will spend a few minutes in the oven on top of the gratin. Remove the pan from the heat and stir in the chopped fennel fronds.
Assemble the dish
Position a rack in the upper third of the oven and preheat the oven to 350 degrees. Pour the cheese sauce over fennel (very gently reheat sauce if cold), and sprinkle with Gruyère and Parmigiano-Reggiano. Bake until bubbling until bubbling and beginning to brown, 15 to 20 minutes.
Remove the baking dish from the oven and scatter the topping in an even layer across the top. Continue to bake the gratin until it takes on a deep golden hue, about 5 minutes. If it needs more color, place dish under the broiler for 1 minute, watching it very carefully to ensure nothing burns. Serve immediately.
