Put oil in a bowl. Pluck the thyme leaves from the stems and add them to the oil. Peel the garlic, press through the garlic press and add. Season with salt and pepper. Slice the feta cheese and marinate in the garlic oil for about 3 hours.
Clean and wash the leek and mushrooms. Cut leek into thin rings, mushrooms into slices. Remove 2 tablespoons of garlic oil and heat in a pan. Fry the mushrooms briefly in it.
Season with salt and pepper. Remove from the pan. Briefly sauté the leek rings and lentils in the frying fat. Pour on the stock and let it swell for about 10 minutes. Drain the sheep's cheese and collect the oil.
Add mushrooms to the lentil vegetables. Stir in vinegar and 4 tablespoons of garlic oil. Spread the lentil salad while still warm on four plates. Arrange the feta cheese on top.