If desired, toast the chopped walnuts. Coarsely chop 4 oz of the chocolate and set aside. Microwave remaining chocolate in large bowl and microwave on high for 40 second intervals until chocolate is melted and stirring frequently.
To the bowl of melted chocolate add sugar, butter, eggs and vanilla and stir until well blended. Add flour and baking powder, mix well.
Stir in chopped chocolate and walnuts
Drop by rounded tablespoons (I use the 1 ½ inch cookie scoop) onto parchment lined baking sheet.
Bake 12-13 minutes or until cookies are puffed and shiny. Cool 1 minute, remove to wire rack to cool completely. Personally I love mine warm with milk!