1. Preheat oven to 350 deg f. Grease a 9 x 13 metal baking pan. 2. Prepare chocolate batter: In a heavy 3 quart sauce pan, over low heat, heat butter and chocolate until melted and smooth, stirring frequently. Remove pan from heat. With a wooden spoon beat in sugar and eggs until well blended. Stir in flour, vanilla, and salt; set aside. 3. Prepare peanut butter batter: In a large bowl, with mixer on medium speed, beat peanut butter and butter until blended. Add sugar, flour, baking powder, vanilla, salt, and eggs. Beat well. 4. Spoon peanut butter batter by heaping tablespoons into baking pan. Pour chocolate batter over the top, spreading evenly with spatula. With a knife, cut ands twist through batters to obtain a marble effect. Sprinkle with chopped nuts. 5. Bake 45 minutes or until toothpick inserted in middle comes out clean. Cool on wire rack, in baing pan. 6.When cool, cut into 4 strips (lengthwise) and 6 strips (crosswise) to make 24 servings. Store in tightly closed container. 7. Each serving = 285 calories, 16 g fat, 53 mg chol, 260 mg sodium. . . Each serving = 50% calories from fat.