Peel the carrots and grate finely. Wash, clean and finely dice the peppers, peel and finely chop the onions.
Mix the sour cream with the salt, pepper, mustard and 2 - 3 tablespoons of vinegar. The amount of vinegar depends on the acidity of the vinegar and personal taste.
Mix the carrots, peppers, onions and the dressing together well and let the salad soak in the fridge for an hour. Then season again to taste and add salt if necessary.