Preheat the oven to 180°C, and line a baking sheet with non stick paper.
Put the butter and sugar in a bowl and beat until fluffy.
Melt 75g of the chocolate. Chop the remaining chocolate into little chunks.
Add the melted chocolate into the butter mixture and mix until smooth.
In a separate bowl sift the flours, cocoa and baking powder. Beat it into the chocolate mixture. Stir in the chocolate chunks.
Drop teaspoon size balls onto baking sheet, press down slightly. Bake for 20-25 minutes until crisp on the outside. They may be a little soft in the middle--this is the melted chocolate. Allow to cool on the tray.