Preheat oven to 385 degrees F (195 degrees C).
Prepare the Broccoli Rabe (1 bunch) by shaving the stems with a vegetable peeler, pulling off the large leaves, and snapping off each floret. Then spiralize the Fennel Bulb (2).
Add the fennel, broccoli rabe, Garlic (5 clove), Shallot (2), Kosher Salt (1 teaspoon), Black Peppercorns (1 teaspoon), Olive Oil (1 tablespoon), and Fresh Thyme Leaves (1 tablespoon) to a large bowl.
Toss to coat. Add Gruyère Cheese (1 cup) and mix well.
Add the mixture to your baking dish. Press down on the mixture to create more room. This mixture will cook down by about half in the oven.
Top with the Gruyère Cheese (2 cup) and the Parmesan Cheese (1 cup).
Bake 30 minutes until the cheese just barely starts to brown.
Let cool for 5-10 minutes before serving. Enjoy!