Make a white sauce by mixing the oil with the flour into a mixture that resembles breadcrumbs.

Now add about a quarter of the milk and stir into a smooth paste.

Put the sauce onto a medium heat, add the rest of the milk and keep staring until the thicker source is formed. Set aside and leave to call slightly. Grate in the grana padano cheese.

Wash your spinach And stir it in to the ricotta cheese. Now gently heat in a wide base pan so the spinach welts. Grate in the nutmeg and black pepper.

Place a layer of spinach and ricotta mix into the bottom of your lasagna dish. Now layer with slices of courgette, then lasagna sheets, then white sauce. Repeat the layers and top with grated cheese.

Bike at 180 C fan for 40 minutes or until the source is bubbling and the lasagna sheets feel cooked when you poke them with a skewer