1. To make the cake layers, prepare three 8 inch cake pans with parchment paper circles in the bottom and grease the sides. Preheat oven to 350°F (176°C).
2. Combine the flour, baking powder, cinnamon and salt in a medium sized bowl and set aside.
3. Add the butter, brown sugar and vegetable oil to a large mixer bowl and beat together until light in color and fluffy, about 3-4 minutes. Do not skimp on the creaming time.
4. Add the eggs two at a time and mix until completely combined. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
5. Add half of the dry ingredients to the batter and mix until combined.
6. Add the vanilla extract, milk and applesauce and mix until well combined. The batter will look a little curdled, but that’s ok.
7. Add the remaining dry ingredients and mix until well combined and smooth. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated. Do not over mix the batter.
8. Fold the chopped apples into the batter.
9. Divide the batter evenly between the cakes pans and bake for 23-26 minutes, or until a toothpick comes out with a few crumbs.
10. Remove the cakes from the oven and allow to cool for about 2-3 minutes, then remove to cooling racks to cool completely.
11. While the cakes bake, make the filling. Melt the butter in a medium sized saucepan.
12. Add the brown sugar, apple sauce, cinnamon and cornstarch and whisk constantly over medium-low heat until sugar is dissolved.
13. Increase heat to medium and bring to a boil. Allow to boil for 3 minutes.
14. Remove from heat and allow to cool to room temperature.
15. Add the sifted powdered sugar and whisk until well combined and smooth.
16. When you’re ready to build the cake, make the frosting. Add the butter and shortening to a large mixer bowl and beat until smooth.
17. Add about half of the powdered sugar and mix until well combined and smooth.
18. Add the vanilla extract, cinnamon and 2 tablespoons of water or milk and mix until well combined.
19. Add the remaining powdered sugar and mix until well combined and smooth.
20. Add additional water or milk as needed to get the right consistency.
21. To put the cake together, trim the tops/domes off of each cake, if needed. Place the first layer of cake on a cake plate or cardboard cake circle. Do be gentle moving the cake layers around – they are very moist and tender. I often use a cake lifter to help with moving them.
22. Pipe a dam of frosting around the outer edge of the cake and fill it in with about half of the filling. Spread the filling and dam into an even layer.
23. Add the second layer of cake, then repeat another layer of dam and filling.
24. Add the final layer of cake on top and then add a thin crumb coat of frosting to the outside of the cake.
25. Frost the outside of the cake with the remainder of frosting. See my tutorial for frosting a smooth cake. 26. Use an icing smoother with a patterned edge to create the lines in the side of the cake.
27. Press the crushed up apple chips into the bottom of the cake.
28. Add some swirls of frosting around the top edge of the cake, then finish it off with apple chips.