Instructions

1. Warm the milk.
   
2. Peel the potatoes, wash them, and slice them thinly.
   
3. Wash the zucchini, trim them, and slice them into 3-5 mm (1/8 to 1/4 inch) rounds.
   
4. In a small saucepan, melt the butter over low heat.
   
5. Add the flour and mix well until you get a smooth paste.
   
6. Increase the heat slightly and cook until the flour turns golden.
   
7. Add the milk, salt, and nutmeg, and cook over medium heat until the béchamel starts to thicken.
   
8. Butter the baking dish and sprinkle with breadcrumbs.
   
9. Layer the potatoes and sprinkle with a bit of salt. Cover the potatoes with a couple of tablespoons of béchamel.
   
10. Add a layer of zucchini, sprinkle with salt, and cover with béchamel.
    
11. Continue layering until all the ingredients are used up.
    
12. Bake in a preheated non-ventilated oven at 180°C/350°F for about an hour (160°C/320°F for 45-50 minutes in a ventilated one). Ten minutes before it's done, sprinkle the casserole with grated cheese.