Clementine cocktail

Method

1. To make the clementine syrup, pour the juice into a pan with the sugar, heat gently until the sugar has dissolved, then bubble for a good 10 minutes until it has reduced by a third and has started to go syrupy. Remove from the heat, strain through a fine sieve and set aside to cool completely.
2. Divide the clementine syrup evenly among 8 champagne glasses (just over 1 tbsp in each) and top with champagne or prosecco, finishing each with a dash of Campari (about 2 tsp or to taste).