Distribute the mixture into muffin forms. Press with a spoon and put them in the fridge.
Melt the chocolate in a water bath. Beat the cream. Soak the gelatin in water, strain it and put it in warm milk. Stir until it dissolves completely.
Once the chocolate cools, add the gelatin to it and stir well. Gradually add the whipped cream and stir carefully with a spatula.
Take the forms out of the fridge and distribute the mousse into them, but don't fill them up all the way. Return to the fridge for about 2 hours. Once the mousse hardens, prepare the glaze.
Crumble the dark chocolate and dissolve it in a water bath with 2 tbsp milk. Add the butter and stir. Once the butter melts, pour the glaze over the muffins.
Store in the fridge and remove from the forms upon serving!