Break the chocolate into small pieces and melt gently using a double boiler or short microwave bursts until smooth and glossy.

Prepare an ice bath by filling a larger bowl with ice and a bit of water.

Place the bowl of melted chocolate over the ice bath and whisk continuously (by hand or electric mixer) until it thickens into a mousse-like texture. Stop when it's thick, soft, and slightly fluffy.

Spoon the mousse into serving bowls and chill in the fridge for 20–30 minutes until fully set.