How to cook
1. To make the layers, beat the eggs with the sugar to a light, fluffy cream. Pour in the rum, freshly brewed but slightly cooled coffee and the teaspoons of Nescafe granules. Beat again until the coffee dissolves and you obtain a homogeneous mixture.
2. Sift the flour and baking powder, add them in lots to the mixture while stirring with a spoon. You can use a mixer instead but don't beat too much because the layer may not fluff up if you do.
3. Pour and distribute the mixture evenly onto oiled baking paper in a baking tray. Bake at 392°F (200 °C) (preheated) for 8-10 min., be careful not to over-bake to prevent it from drying out and crumbling when you try to roll it up.
4. Immediately after taking it out of the oven, invert onto a moist, clean towel, wrap into a roll and cover it.
5. For the filling, beat the egg yolk with the powdered sugar and vanilla sugar, then add the mascarpone and beat to a smooth cream. Unroll the somewhat cooled roll and smear it evenly with the cream. Roll up again and leave to cool completely.
6. For the couverture, mix the mascarpone and Dulce de leche. Smear the surface of the roll, smoothing it out carefully with a spatula.
8. Upon serving, cut the slices with a moistened sharp knife and use the spatula for support because due to the soft couverture you can't really use your hand directly.
A really tasty cake I hope you like!