Sift together flour, coco powder, salt and baking soda. (I used a little baking soda despite the self raising flour because I feel it gives the flour that extra umph to rise well but you can leave it out)

In a mixing bowl, beat together butter and custer sugar until smooth and fluffy. Add in eggs one at a time and mix.

Add in vanilla essence and mix.

Butter is ready for the oven. Preheat your oven to 170°C and bake for 35-40 minutes or until a wooden skewer inserted comes out clean.