In a large mixing bowl, cream together your softened butter and sugar until combined.
Add in the flour and mix together, the consistency should be like a moist play-dough!
Scatter your chocolate buttons into the dough, break some in half to vary the spread.
Once combined, press the dough into a baking tray and level out lightly. The dough fills half of a 9x9 baking tray, double the ingredients to fill this size tray.
Bake at 180 degrees for 20-25 minutes until the top is golden around the edges.
Leave to cool and sprinkle with sugar.
