Clean, wash and cut leek into rings
Heat 1 tablespoon of fat. Sauté the leek for about 5 minutes. Take out some leek for garnishing
Dust the rest of the leek with flour, sauté while stirring, deglaze with a good 3/4 l water and bring to the boil. Stir in stock. Let the soup simmer for about 5 minutes. Melt cheese in flakes while stirring
For the croutons, dice the toast. Heat 1 tablespoon of fat in a frying pan. Roast the bread cubes in it while turning them golden brown and take them out
Puree the soup with the cutting stick. Season to taste with salt, pepper, possibly caraway and white wine. Arrange leek soup in plates. Sprinkle with the croutons and remaining leek rings