In a saucepan, mix 300 ml of champagne with sugar and gelatin. Leave on for 2 minutes to soften the gelatin.
Put the saucepan on a small fire and cook for 2 minutes, stirring constantly, until the gelatin is completely dissolved. Remove from heat and pour the remaining 150 ml of champagne. Shuffle. Pour the liquid into the mold and place it in the freezer for at least an hour.
To get the jelly out of the mold, dip the mold in warm water and go with a knife along the walls of the mold. Then gently flip the form. Cut with a sharp knife into small squares. Sprinkle with sugar, sparkles. Insert holiday skewers.