Preheat oven to 180oC. Line a 24cm square baking tin with greaseproof paper.
In a large bowl over some simmering water, melt the butter & chocolate untill smooth. Add nuts & stir together.
In a seperate bowl, mix together cocoa powder, flour, baking powder & sugar, then add this to the chocolate mixture. Stirl together well. Beat eggs & mix in untill you have a silky consistency.
Allow to cool slightly & add white buttons.
Pour brownie mix into lined baking tray & place in oven for around 25mins. The brownies should be slightly springy on outside but still gooey in the middle.
Allow to cool in the tray, then carefully transfer to a board to cut into squares. Serve with a dollop of creme fraiche mixed with orange zest or ice cream.
