Cocoa brownies

This recipe is so simple, requires very basic ingredients, and has come out perfectly both times I've tried it. What's more, it only uses a single bowl!

5oz/140g unsalted butter
10oz/280g sugar
3oz/85g unsweetened cocoa powder (eg Green & Blacks)
quarter tsp salt
half tsp pure vanilla extract (I used double this, as it was the fake stuff)
2 large eggs, cold
2.5oz/66g plain flour
walnut or pecan pieces (optional)

Put the cocoa, butter, sugar and salt in a heatproof bowl and put in a pan of water to heat gently till all the butter is melted. The mixture is pretty gritty at this stage but don't panic, it will smooth out when you add the rest of the ingredients.

Remove and cool slightly till it is warm rather than hot.

Add the vanilla extract, then beat in the eggs vigorously, one at a time, using a wooden spoon. When the mixture is thick, shiny and well-blended, add the flour and stir it in well. At this stage the mixture becomes quite hard work to stir.

Mix in the nuts then spread the mixture evenly into an 8" (200mm) square tin which has been lined with greaseproof paper.

Bake in the lower half of the oven at gas 3, 170 degrees C, for about half an hour until a toothpick inserted in the centre of the brownie mix comes out slightly moist. Let them cool completely on a rack before cutting (or you can even put it in the freezer/fridge if you are anal about having clean cut lines).

Recipe originally from Smitten Kitchen.