Beat the eggs and sugar lightly with a wooden spoon, until well mixed.

Put the butter and cocoa powder in a heat proof bowl and mix, over a pan of boiling water, till the butter and cocoa becomes a smooth paste. Remove from heat. Allow to cool for 5 minutes.

Add the cocoa-butter paste to the egg-sugar mixture and mix lightly. Now add the flour, baking powder, vanilla and chopped nuts. Fold lightly till everything is well mixed.

Pour the batter into a parchment lined 8-inch square tin. Bake at 190C (375F) for 20 to 30 minutes till the brownie is done. Allow to cool a bit, remove from the tin and finish cooling on a rack.

Cut and dust with powdered sugar if you prefer. I have a 7-inch square tin which is what I use to make my brownies so they are little thicker.