Peel the cucumbers and cut them in half lengthwise. Scrape out the seeds with a spoon. Dice cucumbers finely. Peel and chop onion. Wash the dill. Cut the stalks finely, put the little flags aside.
Heat 1 tablespoon of oil in a saucepan and sauté the onion. Add cucumber cubes and dill stems, sweat briefly and deglaze with stock. Cover and simmer for about 10 minutes. Lift out 1/3 of the cucumber cubes. Stir cornflour into 2 tablespoons of water until smooth, thicken cucumber soup with it, bring to the boil and remove from the stove. Stir sour cream and buttermilk into the soup and puree everything with a chopping stick. Season to taste with salt, cayenne pepper and vinegar. Chill for about 1/2 hour. In the meantime, dice small pieces of toast bread. Fry in 1-2 tablespoons of oil in a pan while turning until golden brown. Drain on kitchen paper and let cool down. Wash, clean and finely dice the peppers.
Chill for about 1/2 hour. In the meantime, dice small pieces of toast bread. Fry in 1-2 tablespoons of oil in a pan while turning until golden brown. Drain on kitchen paper and let cool down. Wash, clean and finely dice the peppers. Clean, wash and finely chop the spring onion. Chop the dill flags finely, except for something to garnish, and stir into the soup. Arrange cucumber soup in cups, sprinkle with croutons and diced vegetables and garnish with dill flags