Preheat oven to 180°C and line a baking tray with baking paper.
Place butter and chocolate in a heatproof bowl set over a saucepan of simmering water (don’t let bowl touch water) and stir until melted. Remove from heat and set aside to cool slightly.
Meanwhile, whisk eggs, vanilla and sugars with electric beaters until thick and pale. Add the chocolate mixture and stir to combine. Stir over the flour, cocoa and spices, and fold to combine, then fold in the chocolate chips.
Place a tablespoonful of dough, 4cm apart, on the tray. Bake, rotating tray halfway, for 14 minutes or until set. Cool on the tray for 5 minutes, the transfer to a wire rack to cool completely.