Soak the gelatin sheets in a small bowl with cold water.
Then, with an electric whisk, whip the egg yolks with 100g (3.5 oz) of sugar for about 6-8 minutes until it becomes light and frothy cream.
Then add the 1/2 cup of coffee (175 ml), the vanilla seeds, and the gelatin, that you squeezed and melted in a saucepan with 50 ml (2fl oz) of cream.
In a bowl, whip the 450 ml (16 fl oz) of cream with 100g (3.5 oz) of sugar.
Add the whipped cream to the coffee cream, mix it well from top to bottom making sure not to disassemble the whipped cream.
At this point our mousse is ready.
Spoon it into lovely custard cups and cover them with transparent paper.
Let them rest in the fridge for at least 1 hour.
Before serving, you can garnish the mousse with chocolate chips or powdered cocoa.