Clean and wash the leek and cut into thin rings. Heat the oil in a pot and sauté the leek in it while turning. Sprinkle in onion soup powder and pour on 1.5 l water. Bring to the boil while stirring occasionally and simmer for about 8 minutes.
In the meantime, fry the ham in a pan without fat until crisp, take it out and keep it warm. Put bread on a baking tray, sprinkle with cheese. Bake in a preheated oven (electric cooker: 175 °C/ circulating air: 150 °C/ gas: see
manufacturer) bake for about 2-3 minutes until golden brown
Wash the thyme, shake dry and pluck. Serve the soup, add the diced ham. Put a slice of bread on each. Garnish with thyme.