Preheat the oven to 350 degrees F. Lightly grease two baking sheets (or line with parchment paper or silpat mats).
Melt the chocolate and butter together (using microwave or in a bowl set over simmering water), stirring until smooth. Set the mixture aside to cool.
In a medium bowl, use an electric mixer to combine the brown sugar, eggs, vanilla, baking powder and salt. Beat in the melted chocolate, then stir in the flour, toffee bits and chocolate chips.
Drop the dough by the tablespoonful onto the prepared baking sheets. Bake the cookies for about 12 minutes, or until the tops are cracked and dry but the cookies are still soft to the touch. Don't overbake! They'll become more firm as they cool.