Set the oven to 175C (350F) and line a 8 x 8 inch baking tin with baking paper.
Melt together the chocolate & butter. You can do this in the microwave in 20 second intervals. Zap for 20 seconds. Mix well. Repeat until it is melted together. This shouldn’t take more than 2 minutes total. Try to limit the microwaving as much as possible and melt more by giving it a good mix in between microwave bursts, otherwise you risk giving it a burnt flavour.
Lightly beat the eggs. Continue beating on low speed while adding the sugar, vanilla and finally the melted butter & chocolate mix. Mix until it is all incorporated.
Whisk together the sifted flour, baking powder, salt and cocoa. Add the flour to the egg mix in 3 parts. Beat gently each time until the flour is just mixed through. Fold through most of the chocolate chips, holding back about half a cup to sprinkle over the top of the brownies.
Spread the batter over the pan evenly, then sprinkle the additional chocolate chips over the top. Bake in the oven for 20 minutes until a toothpick comes out with just a few crumbs. These are definitely best underdone than overdone.
Allow to cool in the tin before cutting into 20 squares.