In a large bowl, mix together the butter, icing sugar, almond powder, cocoa powder and pinch of salt. You can do this by hand or using an electric hand mixer. Add the egg. Stir in the flour until you have an evenly combined mixture. Transfer to plastic wrap and roll up in the shape of a sausage (about 2 inches in diameter). Chill in the fridge for at least two hours.
Heat oven to 300˚F. Line two baking trays with parchment paper.
Mix together the sugar and fleur de sel and spread onto an unlined baking tray. Remove your chilled dough from the fridge and unwrap it. Roll the sausage shaped dough in the sugar and salt mixture. Once the outside is completely covered, slice the dough into 1/4 inch rounds and lay flat on the lined baking trays. Bake in the oven for 20-25 minutes. The biscuits should look dry on top when done. Allow to cool on the sheets for five minutes and then transfer to a wire rack to cool completely.
Store in an airtight container.