Make each of the mixtures for the balls separately, as follows.
Grate the cheese finely, add 4 tbsp flour to it. Beat 1 egg and add it to the cheese.
Extinguish 1 tsp baking powder in 1 tsp lemon juice, add it and knead a smooth, sticky dough.
Put the mixture in the fridge to sit for 30 min.
Grate the feta cheese and make this mixture the same way as above but this time use an extra 2 tbsp flour because feta cheese is a bit more watery. Leave this mixture in the fridge for 30 min. as well.
Use wet hands to form walnut-sized balls from the separate mixtures.
Heat a casserole with generous amounts of oil and drop the balls to fry in it until golden.