HEAT oven to 350°F. Coat 8-inch square baking pan with no-stick cooking spray.
BEAT 1/2 cup peanut butter, butter and sugar in large bowl with electric mixer until creamy. Add eggs and vanilla. Beat until blended. Add milk and pancake mix alternately, beating after each addition until just combined. Pour into prepared pan.
BAKE 30 to 35 minutes or until toothpick inserted in center comes out clean. Cool 10 minutes, then turn cake into a large bowl and set aside. Beat 1/2 cup peanut butter and frosting until smooth. Line two large baking sheets with wax paper.
CRUMBLE cake into fine crumbs with fork in bowl. Add frosting mixture. Mix thoroughly with spatula. Cover with plastic wrap and freeze 30 minutes. Roll mixture into 1 1/2-inch balls using small cookie scoop (one tablespoon cake mixture). Place balls on one prepared baking sheet. Cover with plastic wrap and freeze 1 hour.
PLACE chocolate chips and shortening in microwave-safe bowl. Microwave on HIGH 2 minutes. Stir. Microwave in additional 10 second intervals until completely melted and smooth when stirred.
REMOVE ten cake bites from freezer at a time, keeping the remaining ones frozen. Drop one cake bite at a time into melted chocolate. Spoon chocolate over each bite until coated. Lift cake bite out of chocolate with a fork, allowing the excess chocolate to drip into bowl. Using toothpick, gently push bite off fork onto other prepared baking sheet. Top each with chopped peanuts immediately. Repeat to coat remaining bites. Chill 5 minutes or until chocolate is set. Allow to come to room temperature before serving.