How to Make It
Prepare the Cake Layers: Preheat oven to 350°F. Combine sugar, oil, sour cream, milk, vanilla, pumpkin pie spice, eggs, and pumpkin in a large bowl; beat on low speed with an electric mixer until smooth. Add cake mix; beat on medium speed for 2 minutes. Stir in toffee bits. Spread batter in a greased (with shortening) and floured 13- x 9-inch baking pan.
Bake in preheated oven until a wooden pick inserted in center comes out clean, 28 to 33 minutes. Cool completely in pan on a wire rack, about 1 hour.
Prepare the frosting: Beat cream cheese and butter on medium speed with an electric mixer until smooth. Beat in pumpkin pie spice and vanilla. Gradually add powdered sugar, beating on low speed until smooth and creamy. Spread frosting over cooled cake. Garnish with chopped toffee bars.