1. To make the gold glass rim: mix 1 tsp edible gold dust with a few drops of elderflower liqueur to form a thick liquid.
2. Dredge the rim of the martini glass in the liquid to coat edge making sure the gold liquid is thick enough so that it doesn’t drip. To thicken, add more gold dust and to dilute, add more elderflower liqueur.
3. Pour the elderflower liqueur and lemon juice and 1/2 tsp of edible gold dust into a cocktail shaker and shake until well chilled.
4. Pour into gold rimmed martini glass and top with chilled Champagne.