1 box Betty Crocker™ Super Moist™ yellow cake mix
1 cup milk
1/2 cup butter, melted
3 eggs
1 box (3.4 oz) Jell-O™ butterscotch-flavor instant pudding & pie filling mix (dry)
Frosting:
1/2 cup dark chocolate chips
1/2 cup butterscotch chips
1 1/2 cups butter, softened
3 1/3 cups powdered sugar
3 tablespoons milk
1 1/2 teaspoons vanilla
1/2 cup coarsely crushed mini pretzel twists
Toppings:
1/3 cup caramel sauce
1/2 teaspoon coarse sea salt
Heat oven to 350°F (325°F for dark or nonstick pans). Spray bottoms and sides of 3 (8-inch) round cake pans with cooking spray; line with cooking parchment paper. In large bowl, beat Cake ingredients with electric mixer on medium speed 2 minutes, scraping bowl occasionally. Pour 1 2/3 cups batter in each pan. Spread evenly. Bake 20 to 23 minutes or until toothpick inserted in center comes out clean. Cool 10 minutes; remove from pans to cooling racks. Cool completely, about 1 hour. In small microwavable bowl, microwave chocolate chips and butterscotch chips uncovered on High 60 seconds; stir halfway through. Continue to microwave in 15-second increments, stirring after each, until chips can be stirred smooth; cool 10 minutes. In large bowl, beat 1 1/2 cups softened butter and melted chips with electric mixer on medium speed until blended. On low speed, beat in powdered sugar, milk and vanilla, scraping side of bowl occasionally, until smooth and creamy. Place one cake layer on serving plate. Spread 2/3 cup of the frosting on top; top with second cake layer. Spread 2/3 cup of the frosting on top; top with third cake layer. Frost side and top of cake with remaining frosting. Press crushed pretzels along bottom edge of cake. Refrigerate uncovered at least 1 hour. When ready to serve, carefully pour and spread caramel sauce over top of cake, allowing some to drip down sides; sprinkle sea salt on top. Cover and refrigerate any remaining cake.