Preheat oven to 180 degrees celsius (160 fan-forced).
Grease and line an 18X28cm rectangular slice tin with baking paper.
Place plain flour, salt, baking powder and cocoa powder into the TM bowl. Soft by pressing Turbo 3-4 times. Set aside in a seperate bowl.
Place the butter and chocolate melts into the TM bowl.
Melt on 50 degrees, 4 minutes, Speed 2.
Add the sifted dry ingredients, the brown sugar, white sugar, milk chocolate chips and eggs and mix on Reverse Speed 2.5 for 10 seconds (you may need to use the spatula to assist).
Scrape down the sides of the bowl and repeat for a further 15 seconds.
Pour into the prepared tin and bake for 25-30 minutes or until a skewer inserted into the middle comes out clean.