For the dough, mix the coffee, soluble espresso powder and rum together and leave to cool. Cream butter with 100 g sugar and salt in a food processor for at least 8 minutes.
Then stir in the yolks one at a time. Combine flour, cocoa, nuts and baking powder, stir through with a whisk (replaces sifting) and stir into the foam mixture alternately with the coffee mixture, but quickly and in slow speed of the machine.
Beat egg whites until stiff, add remaining sugar by tablespoonfuls and beat until greasy and glossy. Stir 1/3 of the whipped cream into the flour mixture, then fold in the remaining 2/3 with a spatula. Pour the dough into a greased pan (good 2 liters capacity) and bake at 165° for about 50 minutes.
Bring the coffee liqueur with the orange juice and 1 teaspoon of coffee powder to the boil.
Pierce the still hot cake several times with a knitting needle and drizzle with the mixture.
When cool, frost with cake icing and decorate with mocha beans.
Even if the cake is not soaked, it is moist!
