Whisk together eggs and sugar until foamy, add spoonfuls of mascarpone and mix until the ingredients are completely blended. Gradually stir in the oil and milk.
Mix flour, baking powder, starch flour and cocoa, sift and fold under the egg-mascarpone mixture.
Pour the dough into a greased bundt pan and bake in a preheated oven at 180°C for about 45 minutes.
Remove the cake and let it cool completely before flipping the pan upside down to get it out of the pan.
Sprinkle with powdered sugar before serving.