Make sure all the ingredients are at room temperature.
Grease & line a 6 inch pan. Alternately grease & dust some cocoa evenly. Invert the pan to remove excess. To make layers for black forest cake you can also use two 6 inch pans.
Preheat the oven at 170 C for at least 15 mins
Sieve together cocoa, flour, baking powder & salt to a mixing bowl. Ensure all of them have mixed well. Set this aside.
Break 2 whole eggs to a large mixing bowl. Separate 1 egg yolk and add it as well along with sugar.
Begin to beat on a low speed to avoid splashes. Then increase the speed to high and beat until frothy.
Then pour vanilla & continue to beat until a ribbon consistency is achieved. The eggs turn frothy & foam up. The volume will more than double and will reach a ribbon stage.
Lift the whisk & check to find the ribbon consistency. The egg mixture will fall like a ribbon from the whisk when you lift it. If this is not achieved then continue to beat.
Pour vanilla. Next keep beating and pour oil in a slow stream to the egg mixture. Beat the mixture on a high speed just until combined. Do not over beat.
The flour needs to be added in 3 small batches. Now sprinkle ⅓ of the cocoa & flour to the egg mixture.
Using a whisk gently mix just until partially incorporated. Do not over mix or beat the batter at this stage as it deflates the mixture & can make a flat dense cake.
Repeat adding another ⅓ portion of the flour and mix. Finish off by adding the last part. Mix until just combined well.
Transfer to the prepared pans. Tap the pan to the counter twice.
Bake at 170 C for 15 mins if using two 6 inch pans. Bake for 20 to 24 mins if using a single 6 inch pan.
When the cake is done a tester inserted comes out clean. Transfer the cake pans to a cooling rack and cool down for 15 mins.
Invert on a cooling rack and cool completely.
Dust some powdered sugar or make a frosting. This chocolate sponge cake can be used to make black forest cake or just melt some chocolate chips and pour it over the cake.
I melted little over half a cup of choco chips and frosted the cake. Decorated with some chocolate shavings.