Preheat oven to 170C (fan)
Grease & line 20x20cm tin
Melt butter & 100g chocolate in microwave safe dish
Add both sugars to mixing bowl
Pour the chocolate mixture into the sugar and stir until combined
Crack the eggs in and beat until smooth
Sieve the flour and cocoa powder into the batter & stir through
Chop the remaining 200g chocolate into chunks and stir through the batter
Pour the of the batter into the tin, spreading to an even layer
Bake at 170C for 30 minutes
Cool on wire rack for 5 minutes before putting in the fridge to set
Slice in 16 squares and ENJOY
