Dissolve gelatin in cold water and let it swell for about 5 to 10 minutes.
In a medium bowl whisk cream cheese with powdered sugar. Add sparkling wine and mix to combine.
Dissolve gelatin over low heat, pour over the cream cheese mixture and stir to combine.
Whip the remaining 1 cup (240g) chilled whipping cream until stiff peaks form. Add cream cheese champagne mixture and mix until well combined.
Pour champagne mousse over the chocolate mousse and smooth the top.
Cover and refrigerate for at least 4-6 hours or overnight.
Prepare white chocolate stars for decoration. Melt 2.5 oz (70g) white chocolate over bain-marie. Remove from heat and add remaining chopped white chocolate for tempering. Stir until melted.
Spread chocolate evenly into a thin layer on parchment paper. Refrigerate until slightly set, for about 10-15 minutes. Use star cookie cutters to cut the chocolate. Refrigerate until completely set and ready to use. Paint with gold edible powder if desired.
Decorate the cake with white chocolate stars and gold sprinkles.
Before serving, you can add sparklers for a special effect. Enjoy!