Start by melting butter in a large saucepan over medium heat. Stir in minced garlic, chopped sage, rosemary, fennel, and a pinch of red pepper flakes. You’ll know it’s ready when your kitchen smells magical! Whisk in the flour to create a roux, then slowly add the milk and vegetable broth to avoid lumps. Keep stirring until thickened. Stir in Gruyère, Parmesan, and a touch of nutmeg. Set aside to cool slightly.

Combine ricotta, shredded provolone, thawed and drained spinach, basil pesto, and an egg in a large bowl. Mix until everything is well combined. This creamy, herby mixture will bring vibrant flavor to the lasagna.

Spread a thin layer of the béchamel sauce at the bottom of a buttered 9x13 baking dish to prevent sticking. Add a layer of lasagna noodles, followed by the ricotta mixture and more béchamel. Repeat the layers until you've used up all the fillings, finishing with a generous layer of béchamel and remaining Parmesan on top.

Cover the dish with aluminum foil and bake in a 375°F preheated oven for 30 minutes. Remove the foil and bake for another 15–20 minutes, or until the cheese on top is bubbly and golden brown. Let the lasagna cool for 10 minutes before slicing and serving.