Traditional Greek Moussaka recipe (Moussaka with Béchamel)

Name: Traditional Greek Moussaka recipe (Moussaka with Béchamel)
Prep time: 45 min
Cook time: 1 h
Total time: 1 h 45 min
Cuisine: Greek
Ingredients: 6 eggplants; 5 potatoes (optional); vegetable oil (for frying the eggplants); 750g beef or lamb mince (26 oz); 2 red onions (chopped); 2 cloves of garlic (chopped); 1 tin chopped tomatoes (400g / 14oz); 2 tbsp tomato paste; 1 teaspoon sugar; 1 glass of red wine; Pinch of sea salt and freshly ground black pepper; 1 bay leaf; A pinch of cinnamon or one cinnamon stick; 1/4 of a cup olive oil; 900ml milk (31 fl.oz); 120g butter (4 oz); 120g flour (4 oz); a pinch of nutmeg; 2 egg yolks; 100g Parmigiano-Reggiano or Kefalotyri or your favourite hard cheese (3.5oz); salt to taste