Start the oven at 200 degrees Celsius.
Cut the leek in small pieces.
Peel and grate the carrots, the Zucchini, and the potatoes and fry it together with the leek and soya mince until the vegetables becomes soft.
Add the tomato sauce and the spices in the frying pan and let it all get warm, and pour it all in an oven form.
Stir the natural yogurt together with the eggs and pour it over the gratin.
Cut the feta cheese in small pieces and sprinkle it evenly over the yogurt.
Place the gratin in the middle of the oven for 30 minutes.