A few hours before making the cocktail, champagne in the fridge to chill.
In a cocktail shaker filled with ice, add triple sec and cranberry juice. Shake well.
Pour into a champagne flute. Top up with champagne.
Garnish with cranberries, either floating on top or skewered on a cocktail pick or sprig of rosemary.
Notes
Optionally, you can use an orange twist or lemon twist for a garnish if you don't have fresh cranberries.Cranberry juice cocktail is sweeter than pure cranberry juice. There is plenty of sweetness here if you use 100% cranberry juice, but if you like a sweeter drink, you can use a cranberry juice cocktail. For an alcohol-free drink, use orange juice and a non-alcoholic sparkling wine type beverage (like sparkling apple cider) in place of the triple sec and champagne.