Put the ingredients in a bowl and heat in a microwave until the margarine has just melted. Stir well with a balloon whisk and add the egg yolks.
Loosen the egg whites with a hand mixer and add the sugar in 2 batches. Whisk until you can obtain stiff meringue.
Add 1/3 of the meringue into the chocolate mixture and fold in without breaking the air of the meringue. The batter itself is heavy so you don't have to worry too much.
Add the rest of the meringue and fold in so as not to lose the air of the meringue.
I used normal paper for lining the cake tin but it stuck to the cake badly. It might be better to use baking paper.
Drop the cake tin from a high place several times to let the excess air out. Bake in the pre-heated oven to 170°C for about 50 minutes. When a skewer inserted comes out clean, it is ready.
When baking, this cake swells a lot, but after taking it out from the oven, it sinks. It will have big cracks too.
After cooling completely, cover with cling film and chill for half a day or one day. Serve with plenty of powdered sugar.
I served this with whipped cream and ice cream for my mum.
I used this cocoa powder. If you use 180g it might be too bitter. If 130 g it is still quite dark. You can use less sugar about 60 g.
This is a chocolate brownie recipe ID:742212. If you want to use up your old cocoa powder this is the recipe for you.
Story Behind this Recipe
I always try to make things with few ingredients. This time I tried to make a gateau chocolat to celebrate my son getting into a new school by just using cocoa powder. However, I forgot to buy plain flour. I realized that while baking the cake. It was too late. The cake turned out OK without using any flour so I was relieved.
If you use different cocoa powder adjust the amount of sugar. I check the sweetness of the chocolate mixture before I put in the egg yolks. When you check the cake with a skewer, it doesn't come out completely clean. If the skewer is clearly wet bake the cake longer.