Pre-cooked lentils and then drain. Boil the potatoes and peel them after cooking. Slice the onion and carrot cubes, fry them briefly in a hot sunflower oil. Add chopped celery and garlic. Add the lentils, season with salt, herbs and vinegar. Transfer mixture into the pan and stir. Arrange on top of frozen broccoli. Mash the potatoes while still warm. Add the egg and the feta cheese and add salt if needed to taste. Confused mixture well and transfer tray in the other ingredients. Bake in a preheated 180C oven for 30-40 minutes.