Place the cream in a thin-sided bowl and suspend over the gently boiling bain-marie, ensuring that the bowl does not touch the water. Warm the cream, add the chocolate, melt, remove the bowl. Stir with the whisk on a hand mixer until the chocolate has cooled and solidified a little. Spread the mixture out on a sheet of baking paper to a thickness of approx. 1 1/2 cm, cover and chill for at least 2 hrs.
Using a knife that has been rinsed in hot water, cut the chocolate mixture into cubes approx. 1½ cm in size. Mix the cocoa powder, cinnamon and Fleur de Sel in a deep bowl and toss the truffles in the mixture.