Preheat the oven to 392 °F. Finely chop the onion and cut the broccoli into florets.

Melt the butter in a saucepan and sauté the onion until translucent. Add the broccoli and cook briefly.

Meanwhile, make the sauce: melt a little more butter in another saucepan and stir in the flour. Let it dry briefly over the heat, then gradually whisk in the milk a little at a time until you have a smooth sauce.

Turn off the heat and stir in the grated Emmental cheese and the green pesto. Add the sautéed broccoli and season with salt and pepper.

In a baking dish, layer cheese sauce, lasagna sheets, and sauce again. Start and end with sauce, and make sure the lasagna sheets do not overlap.

Sprinkle the last layer with the remaining grated Emmental cheese, spread a little more green pesto over it, and finish with the pine nuts. Bake the lasagna for 20 minutes until golden brown and cooked through.

Finish with the basil leaves. Enjoy!