For the cheese and leek cake, peel and chop the onion. Cut the leek into rings.
Heat the oil and butter in a pan and saute the onion and leek for about 8 minutes. In a bowl, mix flour with baking powder. Fold in the eggs, cream, feta cheese and grated cheese.
Add the onion and leek and the finely chopped parsley. Season to taste with salt and pepper. Pour the mixture into a springform pan and bake at 180°C for about 40 minutes.
Serve the cheese and leek cake.