Preheat oven to 350°F/180°C/Gas 4.
Melt the butter in a large saucepan over medium heat. Sprinkle with flour and whisk into the butter until smooth. Continue stirring and cook for 5-7 minutes or until the roux has turned a light golden color.
Increase the heat to medium-high and slowly whisk in the milk until the mixture is thickened and combined.
Gently simmer over medium-low heat for 10-20 minutes until you achieve a smooth sauce at your desired thickness. Season with salt, pepper, and freshly grated nutmeg.
Heat the olive oil in a large skillet over medium heat. Add the spinach and continue to toss and stir until wilted. Do not overcook. Remove from heat and set aside.
Meanwhile, bring a pot of lightly salted water to a boil. Add broccoli and cook for 2-3 minutes until just tender. Do not overcook.
Drain broccoli in a colander and chop into rustic, bite-size chunks. Add to a mixing bowl with the wilted spinach. Season with salt and pepper and stir to combine.
Add a light layer of the bechamel sauce to the bottom of a 9x13” baking dish.
Next add a layer of the spinach-broccoli mixture, followed by 3 lasagna noodles.
Top the noodles with a layer of bechamel sauce, spinach-broccoli mixture, spoonfuls of ricotta, and mozzarella. Add 3 more noodles and repeat the layers as before, finishing with mozzarella.
Bake uncovered for 20 minutes. Serve with a fresh green salad and freshly grated parmesan cheese. Enjoy!