Bloom the gelatin in cold water.
Heat the milk in a small pot.
Mix the egg yolks with sugar and salt for 2-3 minutes. Pour in the hot milk, mixing all the time, then transfer the mixture back on low heat.
Cook until it reaches 82°C then remove from heat and stir in the gelatin.
Pour the mixture over the chocolate and mix until smooth.
Allow to come to room temperatures then fold in the whipped cream.
Prepare a 20 or 22cm Ø cake ring by lining it with acetate sheets.
Remove the frozen layers from the fridge and place them in the center of the 20/22cm Ø cake ring.
Pour the chocolate mousse around those layers then cover them with mousse.
Be careful as the mousse might spill at the bottom of the cake ring if it’s not properly sealed.
Place the cake in the freezer for a few hours.