Preheat your oven to 180C/ 160C fan/ gas 4 and line the dish or tray your want to cook your brownies in. Measure out your dry ingredients and sieve into a big mixing bowl. Then, chop the butter and dark chocolate into pieces and place into a small saucepan.
You'll then need to melt the butter and chocolate mixture at a low heat on the hob. You can do this in a bowl over hot water on the stove, but I personally have never felt the need to do it this way. As long as you're very careful, patient and melt the mix on a low heat, you shouldn't have any problems. Keep your eye on it and continuously stir it.
Once the chocolate and butter mixture is completely melted and smooth, take off the heat and let cool down. In the meantime, beat the eggs with the sugar and make sure to do this in a big enough bowl. You can use an electric mixer but it isn't essential.
When the chocolate is at room temperature, pour this into the egg mixture. It needs to have cooled down significantly, as not to scramble the eggs. Then combine the wet ingredients with the dry using folding motions and a spatula to make sure everything is evenly incorporated. When the mixture is well combined and glossy, pour this into your lined tray. Once again, use the spatula to make sure you scrape out every bit.
Cook for 25 minutes before checking to see if done. You want the brownie to have a slight crust on the top and to spring back up slightly when lightly pressed. You don't want it to be runny in the middle or to wobble when you shake the tin, otherwise it needs to go back in for a few minutes. You do, however, want it to be slightly gooey and under-baked - don't worry because it will continue to cook as it cools down. Leave to cool down before slicing.