Dissolve each packet of jelly crystals in one cup of boiling water.
Stand until room temperature.
Add 1 cup vodka to each jelly, then pour into shot glasses and refrigerate until set (about 3 hours).
* I actually used almost a cup of vodka for each mix, but topped each up with a liqueur that complemented the jelly crystal flavour-limoncello for the lemon, grand marnier for the lime and cassis for the raspberry. It's really good!