Cook the washed spinach in boiling water until soft: they will cook for about 10 minutes.
Preheat oven to 180°C.
Prepare the bechamel sauce by melting 50 g of butter in a saucepan: add the flour and mix quickly with a whisk or a fork, making it toast well. Add the milk in a thin stream, stirring constantly with a whisk to avoid lumps. When it has thickened, after about 5 minutes, season with salt and add a generous pinch of grated nutmeg.
Blend the well squeezed spinach and mix with the bechamel sauce, 2 free range eggs, the grated Parmesan, a good pinch of grated nutmeg and salt, if necessary.
Butter and dust with breadcrumbs a rectangular cake mould, fill with the spinach and sprinkle the surface with the breadcrumbs and a few knobs of butter.
Bake the flan in the oven for 30 minutes, than grill it for 5 more minutes to brown the surface.