Classic Greek Moussaka - Traditional and Delicious!

Ingredients:
• 3 large eggplants, thinly sliced
• 3 medium potatoes, peeled and sliced
• 1 zucchini, thinly sliced (optional)
• 500 ml olive oil for frying
Ground beef:
• 500 g ground beef or lamb, medium fat
• 500 g grated tomatoes or tomato puree
• 1 onion, chopped
• 1 clove of garlic, minced
• 2 tbsp, tomato paste
• 1/2 tsp ground cinnamon
• 1 tsp ground allspice
• 1 tsp black pepper
• 2 tsp thyme (dried or fresh chopped)
• 1 bay leaf
• 1.5 tsp salt
• 1 tbsp olive oil
• 1 cup chopped parsley (optional)
• 1/2 cup beef stock or water (optional, depending on the juice of tomatoes)
Mornay (Greek Bechamel with egg yolks):
• 100 g olive oil
• 100 g flour
• 1 liter full fat warm milk
• 1 tsp black pepper
• 1 tsp grated nutmeg
• 2 egg yolks
• 150 g graviera or kefalograviera cheese, grated (alt: gruyere, myzithra, parmesan or pecorino)
• 1 tsp salt