Lightly grease a 12- to 13-inch pizza pan. Press cookie dough slices into prepared pan to within 1 inch of the edge of the pan. Bake in a 350 degree F oven for 15 to 20 minutes or until browned and center appears set. Immediately sprinkle with chocolate pieces; drop peanut butter by spoonfuls atop chocolate pieces. Let stand for 5 minutes. Gently spread chocolate and peanut butter over warm crust. Top with chopped candy bars and nuts. Chill for 1 hour or until chocolate mixture is set. Before serving, heat hot fudge topping, if using. Drizzle over pizza. Cut into wedges. Makes 16 servings.