Place the ricotta, sugar and cocoa in a large bowl and mix with an electric whisk (or a hand whisk).
Add the eggs, the cold coffee and the potato starch, mixing well to obtain a smooth mixture.
Line a pan with baking paper and pour in the mixture.
Cook at 160° for about 40 minutes (do the toothpick test but remember that it is a soft mixture, once cooled it will be compact and can be sliced easily).
If you like, complete with icing sugar or whipped cream.
