Grease the bundt cake mould with butter and coat with coarse flour. Pre-heat the oven to 180 degrees.
Add the powdered sugar to a bowl. Crack three eggs and separate the yolks from the whites. Beat the eggs whites until stiff. Add the yolks to the bowl with the powdered sugar, add oil, and beat for two minutes. Add egg cognac, and beat one more minute.
Then add corn starch, semi-coarse flour, baking powder, and mix. Carefully fold in stiffly-beaten egg whites.
Pour the batter into the mould. Melt the chocolate in a double boiler (you can thin it by adding cream), and slowly pour onto the batter. As you pour, mix the chocolate into the batter with a spoon or spatula. Bake in the oven on the bottom rack for 35–40 minutes. Remove the bundt cake from the mould and let cool.
Remember, every oven bakes a little differently, and results also depend on the specific mould you’re using. To check if the cake is done baking, use a skewer or toothpick – if the skewer or toothpick comes out clean, the cake is finished.