Chicken breast with mozzarella

I have this recipe from a friend of mine.
The original recipe is on: http://citromhab.blogspot.hu/, I changed it a bit, but it won’t be fair to say that this is my invention.

Ingredients: 5 cooked potatoes, 8 chicken breast fillets, 2 bigger white onions, a bigger tomato, mozzarella, paprika and oil. 
I cook the potatoes and slice them in round shapes. I grease an oven proof pan with butter and place the potatoes in it with salt. In a sauce pan I heat the oil and cook the chopped white onions. When ready, I add a small spoon of paprika. Put them the top of potatoes.
In the same pan I grill now the seasoned chicken breast. When ready, I put them on the onions, add the sliced tomatoes and the mozzarella. In a preheated oven I cook it for 10-15 minutes.
I served it with pickled carrots.
If I remember well in the original recipe the chicken breast was marinated in greek ingredients.