First, melt the chocolate either by double bath or microwave. In pan bring the milk to a boil and add the gelatine or the Agar Agar. If using Agar Agar make sure your reach a total boil so that it can dissolve completely. If at a high altitude where water boils before 100 C (212 F), use the micro wave to reach the melting temperature.
Pour gradually the milk mix into the chocolate and mix with a “Maryse” as if making a Ganache. With an egg beater beat the cream to become soft and solid. It should be similar in appearance to white eggs. Once the temperature of the chocolate mix has come down o about 45 C (115 F), gradualy and gently mix the beaten cream into the chocolate. Bring it to a uniform color and texture. Leave in the fridge for at leats 12 hours.
This is the only “Mousse” that does not suffer from being frozen.