Heat the water in a saucepan and prepare the pasta. Dice the onion, brown in a little butter in a pan. Cut the ham into pieces, add to the onion. Cut the leek into slices and add to the pan.
Add the cooked pasta and season with salt and pepper. Add the sour cream or cream cheese, season to taste. Halve or quarter the cocktail tomatoes, depending on the size, and place in the pan. Just before serving, add the herbs.