HEAT oven to 350 degrees F. Line bottom and sides of 15 1/2 x 10 1/2 x 1-inch jelly roll pan with foil. Coat with no-stick cooking spray.
BEAT shortening, peanut butter and brown sugar in large bowl with an electric mixer at medium-high speed until creamy. Beat in eggs and almond extract until smooth. Add flour, baking powder and salt. Mix at low speed just until combined. Spread evenly in prepared pan.
BAKE 18 to 20 minutes or until toothpick inserted in center comes out clean. Cool on wire rack while preparing chocolate layer.
PLACE chocolate chips in large microwave-safe bowl. Microwave on HIGH 1 minute. Stir. Microwave in 15 second intervals until melted and smooth. Stir in hot fudge topping. Microwave on HIGH 15 seconds. Spread over warm baked bars. Sprinkle with walnuts. Chill 1 hour or until chocolate layer is firm.
LIFT bars from pan with foil and place on cutting board. Cut into diamonds by cutting on the diagonal from corner to corner both directions forming a large "X". Beginning at one center cut, make 1 1/2-inch parallel diagonal cuts on both sides. Repeat with other center cut to form diamonds. Store in refrigerator.