Cut the broccoli florets and boil them in salted water until cooked (approx. 10 mins), drain and leave to cool.
In the meantime, make the béchamel sauce by melting the butter in a small saucepan over low heat, add the flour and mix well with a whisk until you obtain a smooth and lump-free mixture. Stir in the milk at room temperature, then season with a pinch of salt and grated nutmeg. Cook over low heat for 5-6 minutes, until the sauce becomes creamy.
In a mixer, combine the broccoli with the béchamel, eggs, Grana Padano, breadcrumbs, lemon peel, salt, pepper, and a pinch of nutmeg, and blitz until you obtain a creamy and smooth mixture.
Pour the mixture into a greased baking tin (20cm-22cm) lined with breadcrumbs and bake in a preheated oven at 180°C for 30-35 minutes. Allow to cool down before serving.