One day ahead, make the sirop d’épices. Mix the sugar and water together in a small saucepan and heat over medium-low flame. As it warms up, stir occasionally to dissolve the sugar.
When the sugar is dissolved and the liquid is simmering, stir in the raisins, ginger, vanilla bean, star anise and cinnamon stick. Reduce heat to low and let everything simmer, stirring occasionally, for 5 minutes.
Let cool in the pan, then transfer to a bowl or glass measuring cup and refrigerate covered for about 24 hours. Strain into a lidded jar. You can add the star anise, cinnamon stick and vanilla bean to the jar for the visual effect (or not), but discard the ginger and raisins.
The sirop d’épices will keep for a couple of weeks in the fridge.
Make the cocktail. Combine the rum, egg white, lime juice and sirop d’épices in a cocktail shaker. Shake for about 10 seconds to froth the egg white.
Fill the shaker with ice and shake until very cold, about 20 seconds.
Strain through a fine-mesh strainer into a chilled coupe. (You can also serve the drink over ice in a rocks glass.) Garnish with fruit, if you like. Serve.