A mumsnet classic. Just wanted to say, my latest tweak is to leave out the walnuts and replace with 250 g blueberries (I buy frozen and defrost as they are so much cheaper.) Add an extra 5 mins onto the cooking time.
Rather delicious as the berries cut through the sweetness of the chocolate. Yum 
. Have also posted the recipe for the uninitiated 
Must also add that I put my chocolate and marg/butter together in a bowl and melt in the micro and I don't use an electric mixer and they are still truly scrumptious!
Suzy Wong Brownies
A 7 or 8 inch square tin lined with greaseproof paper/baking parchment and the oven set to 180/GM4 moderate oven.
A small saucepan in to which you put
150g butter
150g chocolate, at least half of it should be plain
On a low heat and let it melt together and leave it to cool slightly
Then beat together in a bowl
2 eggs
1 tsp vanilla extract
175g caster sugar
Until creamy looking, use a hand whisk or an electric one
Then sift in
100g plain flour
1 big tablespoon of drinking chocolate
And a quarter of a teaspoon of salt
Throw in 100g walnuts
And the chocolate and butter and mix well with a spatula, but don't beat it. It should be smooth and glossy.
Scrape the batter into the lined tin and bake it for 18 minutes.
Then have a look at it, the top should be pale and opaque with a couple of cracks starting to emerge like a dried up muddy puddle. The body of the mix will still be slightly wobbly with the edges looking like ordinary cake. If it isn?t like this then leave it in for another 3 minutes or until the first cracks in the puddle surface appear.
Then leave it in the tin to cool for 20 minutes.