Preheat your oven to 375°F / 190°C.
In a large skillet, heat the olive oil over medium heat.
Add the chopped fennel and minced garlic, cooking for 3-4 minutes until tender and fragrant.
Add the spinach, cover, and cook for about 2 minutes more, just until wilted.
Transfer the cooked vegetable mixture to a fine-mesh sieve.
Using the back of a large spoon, press firmly to squeeze out as much excess liquid as possible. This is a crucial step for a creamy filling!
In a large bowl, combine the lightly beaten egg, ricotta cheese, Parmesan cheese, Italian seasoning, and lemon zest.
Stir until well-mixed, then fold in the drained spinach and fennel mixture.
Prepare your baking dish by spreading half of the marinara sauce evenly over the bottom of an ungreased 3-quart rectangular baking dish (a 9x13 inch pan is perfect).
Lay one crepe flat and spoon about 1/3 cup (720 ml) of the ricotta filling down its center.
Roll it up snugly and place it seam-side down in the prepared baking dish.
Repeat with the remaining crepes and filling.
Spoon the rest of the marinara sauce in a strip down the center of the rolled crepes.
Pour the Alfredo sauce over the top, spreading it to cover the crepes.
Finish by sprinkling the shredded fontina cheese evenly over everything.
Bake, uncovered, for 25 to 30 minutes. The dish is ready when the sauces are bubbling around the edges and the cheese is melted and golden.
Let the dish stand for 10 minutes before serving. This allows it to set up, making it much easier to serve.
Don't skip pressing the liquid from the spinach and fennel. A dry filling is key to preventing soggy crepes and ensures a rich, creamy texture.
