Gently melt milk, cream, cooking chocolate and caster sugar over a double boiler.
Soak gelatine leaves in cold water for about 5 mins until soft. Squeeze out any excess water and add to the melted chocolate. Then whisk well until gelatine has dissolved and strain chocolate mixture through a fine sieve.
Transfer mixture to a large dish (or 6 x 100 ml ramekins). Then set aside to cool a little, cover with plastic kitchen wrap and refrigerate for at least 4 hours.
Serve with a good dollop of whipped cream or vanilla ice cream on top.