1. Peel the sweet potatoes and cook for about 20 minutes in a pot of salted water.
2. In the meantime, chop the onions and garlic. Sauté the minced meat with the olive oil in a pan, add the onion and garlic and continue cooking briefly. Add the tomato paste and the oregano and stir well. Season well with salt and pepper.
3. Remove the sweet potatoes from the water, allow to cool and then cut into slices. Place the sweet potato slices in a casserole dish, add the minced meat and some feta. Repeat this step until a few nice even layers have been created.
4. In a tall container, mix the altyn kaymak and the milk well with a whisk and add in the casserole dish.
5. Sprinkle with the grated kashkaval and bake at 200 degrees for about 30 minutes until the cheese is golden brown.