Heat the cream in a saucepan over low heat until it just begins to bubble then immediately take off of the heat.
Place the chopped dark chocolate in a bowl and pour the cream over it.
Stir it until it’s smooth and the chocolate has completely melted.
Stir in the champagne and mix until well combined.
Let the mixture sit at room temperature for 30-45 minutes, then cover with cling film and refrigerate for at least 3 hours.
Dust the palms of your hands with cocoa powder then, using a melon baller or a tablespoon, scoop the chocolate out then roll it between your palms to shape it into a ball.
Place the ball on to a baking sheet lined with baking paper.
Repeat this with the remaining chocolate ganache.
Freeze the truffles for at least 30 minutes or up to 1 hour.
Place the white chocolate in a small bowl and heat in the microwave at 20 second intervals, stirring in between bursts until smooth. Alternatively, place the bowl over a pan of steaming water (but without letting the bowl touch the water) and stir until melted.
Use two forks to dip each chocolate ball in the melted chocolate, allowing the excess to drip off.
Place the dipped truffles on the baking sheet and decorate with the gold leaf.
Chill until set.