HEAT oven to 350ºF. Spray a 13 x 9-inch pan with no-stick cooking spray.
COMBINE shortening and unsweetened chocolate in microwave-safe bowl. Microwave on MEDIUM (50% power). Stir after 1 minute. Repeat at 1 minute intervals until mixture can be stirred until smooth. Stir in granulated sugar. Stir in eggs, one at a time, and vanilla.
COMBINE flour, baking powder and salt in medium bowl. Gradually stir into chocolate mixture. Spread into prepared pan.
BAKE 30 minutes, or until set.
BEGIN preparing topping during last 5 minutes of the bake time for cake. Combine shortening and unsweetened chocolate in microwave-safe bowl. Microwave on MEDIUM (50% power). Stir after 1 minute. Repeat for 1 minute intervals until mixture can be stirred until smooth.
TRANSFER to bowl of electric mixer. Add evaporated milk and granulated sugar. Beat at low speed until well blended. Add powdered sugar and vanilla. Beat until blended.
SPRINKLE marshmallows over hot cake layer. Pour prepared chocolate topping over marshmallows. Drop peanut butter by teaspoonfuls on top of hot chocolate topping. Swirl together using tip of knife. Cover pan immediately with foil. Cool in pan on cooling rack. Cut into 2 x 1 1/2-inch bars.
If topping becomes too firm to pour, reheat on low.
(1 bar of 36)
Calories from Fat80g
Total Fat 9g
Saturated Fat 3g
Polyunsaturated Fat 0g
Monounsaturated Fat 0g
Total Carbohydrates 26g
Dietary Fiber 1g
Vitamin A 0%
Vitamin C 0%
Vitamin D 0%
*Percent Daily Values are based on a 2,000 calorie diet