Heat the grapes, or alternatively 300 ml red grape juice, with the rock candy in a saucepan and crush the grapes. Stir in about half a teaspoon of gingerbread spice and let cool.
Strain the grape juice and pour it into a sealable bottle, add the grappa and shake well.
The liqueur can be drunk straight away, but the longer it stands, the better it gets. Thanks to the gingerbread spice it goes very well with the Christmas season. Filled in small liqueur bottles, the liqueur is also a nice souvenir.