Melt six ounces of the semi-sweet chocolate, the unsweetened chocolate and the butter in a double boiler. In a bowl, beat eggs and vanilla. Gradually add sugar, beat until thickened. Beat in the chocolate mixture. Mix flour, salt, and baking powder. Add to chocolate mixture and stir well. Stir in nuts and chopped chocolate. Drop by rounded teaspoonfuls onto baking sheets and bake at 325F for about 12 minutes.