12 servings | Prep Time: 20 Minutes | Start to Finish: 3 Hours 45 Minutes
1 Line bottom and sides of 5½- to 6-quart slow cooker with 1 piece of cooking parchment paper; trim edges if needed. Spray with cooking spray.
2 In large bowl, beat cake mix, water, eggs, ½ cup peanut butter and the butter with electric mixer on low speed 30 seconds, then on medium speed 2 minutes, scraping bowl occasionally. Remove ⅔ cup of the batter to medium bowl; stir in ½ cup chocolate syrup to make chocolate fudge batter.
3 Spoon one-half of the peanut butter batter into slow cooker. Spoon all of the chocolate fudge batter over peanut butter batter. Top with remaining peanut butter batter. Swirl with a knife in a circular motion.
4 Place folded, clean dish towel under cover of cooker. Cook on High setting 1 hour 45 minutes to 2 hours 15 minutes, carefully rotating slow cooker’s ceramic insert 180 degrees (leaving cover on) after every 45 minutes or until toothpick inserted in center comes out clean. Uncover and transfer ceramic insert from slow cooker to cooling rack. Let stand 10 minutes. Place cooling rack upside down over insert; turn rack and insert over; remove insert. Cool on cooling rack 1 hour.
5 In medium bowl, beat 3 tablespoons peanut butter and 2 tablespoons milk with whisk until smooth. Add powdered sugar; mix until smooth. If too thick, gradually add additional 1 tablespoon milk until glaze is desired consistency. Spread peanut butter glaze over cake. Drizzle with chocolate syrup. Sprinkle peanut butter cups over top of cake.
1 Serving: Calories 460; Total Fat 20g (Saturated Fat 8g, Trans Fat 0g); Cholesterol 60mg; Sodium 450mg; Total Carbohydrate 62g (Dietary Fiber 2g); Protein 8g Exchanges: 1 Starch, 3 Other Carbohydrate, ½ High-Fat Meat, 3 Fat Carbohydrate Choices: 4