Pre heat the oven to 180 C / Gas 4. Line a 7x11 inch tin with baking parchment, we're going to need this for the brownies later.
Put the walnuts on a some tin foil an leave in the oven for exactly 7 minutes.
You're going to need a bowl that you can heat that will also fit into a pot, so it's not touching the bottom, like it's sort of stuck. As shown in the picture.
Fill the pan to the half way mark with water, and bring it to a simmer. Put the bowl over the top and add the butter and chocolate. Wait for the chocolate to melt then use a whisk to make sure it's smooth.
In a separate bowl add the sugar, flour, salt and baking powder and walnuts. Now add the chocolate and butter mixture and stir. Then add the eggs.
The mixture may seem 'granulated' in the fact that if you try it you can feel the sugar. That's normal. Pour the batter into the tin and spread evenly across it.
Put it in the oven for half an hour. Once it's been time, take it out and check to see if it's cooked. If so take it out to cool. Leave it for 20 minutes, just walk away - don't touch it! Then transfer it to a wire cooling rack and leave for another 20 minutes.
Place the brownies on a flat surface and cut in into cubes, I suggest serving warm with some vanilla ice cream. However they are just as awesome cold and on their own.