Cut the chocolate into pieces. Put 5 tbsp cream, 100 g chocolate and 2 tbsp butter in a small pot. Heat while stirring until a smooth mixture is formed. Pour into a bowl and let it cool down for about 10 minutes.
Whip the rest of the cream until stiff and fold into the lukewarm cream.
Layer the cream and puffed rice in four glasses (each containing approx. 200 ml). Cover the glasses and chill for about 2 hours.
Caramelise the sugar in a pot until golden brown. Add milk, 1 tablespoon butter and 50 g chocolate. Stir over low heat to a creamy toffee cream. Let it cool down while stirring occasionally.
Just before serving, spread toffee cream over the cream.