Melt the margarine in a microwave (this usually takes about 3 minutes).
Add the cocoa into the margarine a little at a time and mix until smooth.
Crack the eggs into a separate bowl and whisk them for 3 minutes.
Gradually mix the sugar into the eggs well.
Add the vanilla oil to the eggs and sugar, then pour the cocoa mixture from Step 3 into the bowl too. Combine well.
Sift in the cake flour.
Then fold in the cake flour using a rubber spatula.
Pour the brownie mixture into the pan and even out the surface (the mixture should be quite firm). Bake the brownies in an oven preheated to 160°C for 25 minutes.
Once the brownies have cooled, cut them into slices and serve.
I think that these brownies are relatively sweet, but since they're made with just cocoa they may have quite a mature flavour.
When I take these to children's parties I usually coat them in white chocolate that's been melted in a bain-marie.
I also sometimes cover them in chocolate sprinkles.
Unsalted margarine is ideal for this recipe but lately I've found myself using a low-calorie spread that's been on offer at the shop.
For my friends with a sweet tooth, I tend to add 50-70 g non-melt chocolate chips into the mixture as well.
Story Behind this Recipe
I found the original recipe for these brownies in a children's recipe book. Since then I've modified bits and pieces and have been making these brownies for over 15 years now. I use it a lot for when I have to bring something to parties or when baking for my kid's kindergarten outings.
Even though brownies are usually filled with walnuts, I don't use them in this recipe because some of the children in my family don't like nuts. If you'd like to use them, please add 100 g finely chopped walnuts after Step 6.