Preheat oven to 220C/425F/Gas 7.
Place potato slices into a saucepan of boiling water and cook for 3-4 minutes until just tender.
Drain and place the sliced potatoes onto a non-stick baking sheet in a single layer. Spray with low-calorie cooking spray and season to taste with salt and pepper and half a teaspoon of ground cinnamon.
Place the sliced aubergines onto a non-stick baking sheet in a single layer. Spray with low-calorie cooking spray and season to taste with salt and pepper and half a teaspoon of ground cinnamon.
Put the trays of potato and aubergine slices into the oven to bake for 30-40 minutes, turning halfway until browned.
When the vegetables are cooked, reduce over to 200C/400C/Gas 6.
To make the meat sauce, dry fry the beef mince in a non-stick deep frying pan over medium-high heat until browned. Drain off any excess liquid and set meat aside. Wipe pan with a paper towel.
Return the pan to the heat and spray with low-calorie cooking spray. Fry the onions and garlic for about 5 minutes until softened - add a splash of water if they start to stick.
Add the browned mince back to the pan, crumble in the beef stock cube and stir.
Add the dried mint, dried oregano, and cinnamon - you can add more/less to your personal taste if you wish. Stir.
Add the tomato purée and canned chopped tomatoes and stir everything to combine. Add salt and pepper to personal taste.
Bring to the boil and reduce to a low simmer for 20 minutes.
Meanwhile, make the topping by cracking the eggs into a large mixing jug and beat with a fork. Add the Quark and fat-free Greek yogurt and whisk everything together well. Season with salt and add a handful of the cheese to the mixture. Set aside.
To assemble the moussaka, spray a non-stick baking dish (approx 13" x 9") with low-calorie cooking spray and place half the aubergines in a layer in the bottom of the dish followed by a layer of half of the potatoes.
Pour the meat sauce over the potato layer and spread evenly.
Add a layer of the rest of the aubergines, followed by a layer of the rest of the potatoes.
Pour over the topping and spread evenly.
Sprinkle with the remaining cheese.
Bake in the oven for 30-40 minutes until golden and piping hot.
Serve with a side salad.