Steps

1. 1. In a small saucepan, toast Szechuan peppercorns over low heat until fragrant. Crush them using a mortar and pestle.
2. 2. In a separate saucepan, heat heavy cream until just simmering. Add crushed peppercorns and let steep for 30 minutes.
3. 3. Strain the cream mixture to remove peppercorns and return to the saucepan. Add sugar and vanilla extract, stirring until sugar dissolves.
4. 4. Pour the hot cream over chopped dark chocolate in a bowl. Let sit for a minute, then stir until smooth and glossy.
5. 5. Divide the mousse into serving dishes and chill in the fridge for at least 2 hours before serving.