Preheat oven to 150°C.
Line the bottom and sides of a small springform pan with baking paper.
Place chocolate and butter, both in large chunks, in a bowl. Place the bowl over a small pot or saucepan with boiling water until the chocolate and butter are fully melted, stirring often with a whisk or spatula.
Separate egg yolks and whites. Lightly whisk the yolks until homogenous. Whisk the whites either by hand or with an electric blender until nice and firm.
In a large bowl, place cocoa powder and almond flour, mix well. Add the chocolate mixture, egg yolks and coffee, mix well with a whisk or spatula.
Gently fold egg whites into the batter using a spatula until fully combined.
Place cake pan in the oven. If you have an instant read thermometer, bake until the centre of the cake reaches 92-93°C. This will take approximately 50 minutes.
Turn off oven and leave cake in for an extra 5 minutes.
Take cake off the oven and place on a cooling rack or trivet. When the outside of the pan has cooled down, disasemble and place cake on a dish or board.
Using a fine sieve, dust cake with a teaspoon of cocoa powder, slice and enjoy.