Rinse the vegetables. Remove outer leaves from leek and cut stalk into slices. Peel carrots and cut into slices. Peel potatoes and dice. Peel onions, cut in half and cut into fine dice. Divide the cauliflower into florets and cut in half if necessary. Rinse the yellow peppers, trim, cut in half, remove seeds, remove the white ribs and cut into strips. Cut the celery into slices.
Blanch tomatoes for a few seconds, rinse in cold water, peel, quarter, core and cut into very small cubes. Rinse the parsley, shake dry, pluck the leaves from the stems and finely chop. Bring vegetables with 2 liters (approximately 8 1/2 cups) of water to a boil for 10 minutes and then reduce heat to low and simmer about 25 minutes. Before serving, season with herbs and spices (not salt)!