Wash the lentils, soak them in the unsalted vegetable stock for 3-4 hours and cook until soft in 20-30 minutes. Only then season with herb salt, pepper and fruit vinegar.
Wash the leek, cut into strips, sauté in butter and season with herb salt and pepper. Mix the leek with the cooked lentils, season to taste and pour into a possibly greased baking dish (I don`t grease the dish ).
Lightly roast the sunflower seeds in a dry pan over a mild heat. Scatter the roasted sunflower seeds and grated cheese over the casserole. Finally, spread the sour cream on top and bake at 200 ° C on the second rack from the top in the oven for about 30 minutes.