Place all of the citrus zest and juices in a large pan with the sugar and spices, and bring to the boil. Let the mixture simmer for 15 minutes then, once all of the sugar has dissolved, take it off the heat and leave it to cool to room temperature, allowing the spices to infuse.
Once cooled, strain and chill the syrup in the fridge until you’re ready to serve.
Make the drinks in a blender in batches of 4 so you don’t overload it. Blitz a measure of syrup, a shot each of vodka and limoncello and a handful of ice per person. Ensure that all of the ice is crushed before serving in cocktail glasses.