Prepare the jelly according to the package instructions, but use half the water: if the instructions call for 400 ml, use only 200-300 ml of boiling water.

Pour the jelly into molds and refrigerate until fully set.

Soak the gelatin in 100 ml of cold water to let it swell.

In a bowl, combine the sour cream with the sugar and milk, add vanillin if desired, and mix well.

Cut the set jelly of different flavors and colors into cubes, place them in a pan, and mix.

Dissolve the gelatin on the stove, add a couple of tablespoons of the sour cream mixture to lighten it, then pour the gelatin mixture into the rest of the sour cream mixture and mix quickly.

Pour the mixture over the pan of colorful jelly cubes and refrigerate the cake until fully set. Enjoy!