Melt the chocolate in a bain-marie or in a microwave oven.
In a saucepan, bring the cream to a boil and pour on the melted chocolate in three goes.
At 40°C, add the softened butter and mix.
Cover with a film in contact and put away at room temperature for one night.
The next day, poach balls, 2cm in diameter, with a 10 mm plain pastry bag, or with a melon ball and put away in the refrigerator.