Beat butter or margarine in a large mixing bowl with an electric mixer on medium to high speed for 30 seconds. Add granulated sugar, brown sugar, and baking soda; beat till combined, scraping sides of bowl occasionally. Beat in eggs, unsweetened chocolate and vanilla till combined. Beat in as much of the flour as you can with the mixer. Stir in remaining flour, white baking bar, semisweet or bittersweet chocolate, and, if desired nuts.

Drop 1/4 cup of dough at a time 4 inches apart onto a greased cooked sheet. Bake in a 350º oven for 12 to 14 minutes or till edges are firm. Cool on cookie sheet for 1 minute. Transfer to wire racks and cool completely.