Place peeled onion and fish broth set: head, tail and fins in a saucepan. Pour in water and add bay leaf, allspice, salt. Bring to a boil and cook for 3-5 minutes. Place carp pieces in the saucepan and cook for another 15 minutes over medium heat.
Place the prepared fish pieces in a deep bowl, strain the broth through a sieve and mix with gelatin.
Place carrot pieces and herbs on top of the fish and pour in the broth.
Place the aspic in the refrigerator until completely set.