Preheat oven to 350°F.
Beat brown sugar, butter, eggs, corn syrup and vanilla in large mixer bowl until well blended. Gradually beat in flour, cocoa powder, salt and baking powder. Stir in chocolate chips, toffee bits, and walnuts.
Drop by heaping tablespoonfuls onto greased baking sheets. Lightly press down with the heel of your hand. Bake for 12 to 14 minutes until cookies are set but still soft. Cool on pans for 2 to 3 minutes. Remove to rack to cool completely.