Break up the chocolate into small pieces and add it to a bowl.
Pour in 210 milliliters of boiling water and whisk until the chocolate is completely melted.
In a larger bowl, add two handfuls of ice cubes (around 500 grams) and pour in enough water to reach the top of the ice cubes.
Add the bowl of melted chocolate to the ice bath and whisk for around 5 minutes until it begins to thicken.
Remove the bowl from the ice bath and continue whisking for another 30 seconds until the mousse is ready.
Serve the chocolate mousse, optionally making a quenelle with a heated spoon.
