PREHEAT oven to 350°F. Microwave 8 oz. chocolate in large microwavable bowl on HIGH 2 minutes; stir until chocolate is completely melted. Stir in sugar, butter, eggs and vanilla with wooden spoon until well blended. Add oats and baking powder; mix well. Stir in chopped chocolate, raisins and walnuts.
DROP rounded tablespoonfuls of dough, 2 inches apart, onto ungreased baking sheets.
BAKE 12 to 13 minutes or until cookies are puffed and shiny. Cool 1 minute; remove from baking sheets. Cool completely on wire racks.