1. To make the pecan pie filling, combine all ingredients except the pecans in a saucepan. Heat over medium until it begins to boil, stirring constantly.
2. Add the pecans and allow to boil for 30 seconds.
3. Remove mixture from the heat and refrigerate until cool and thickened.

TO MAKE THE CAKE LAYERS:

4. 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).
5. In a large mixing bowl, cream the butter and sugars together until light in color and fluffy, about 3-4 minutes. Do not skimp on the creaming time.
6. Add sour cream and vanilla extract and mix until well combined.
7. Add egg whites in two batches, mixing until well combined after each. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
8. Combine the dry ingredients in a separate bowl, then combine the milk and water in a small measuring cup.
9. Add half of the dry ingredients to the batter and mix until well combined. Add the milk mixture and mix until well combined. Add remaining dry ingredients and mix until well combined. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
10. Divide the batter evenly between the cakes pans and bake for about 21-23 minutes, or until a toothpick comes out with a few crumbs.
11. Remove the cakes from the oven and allow to cool for about 2-3 minutes, then remove to cooling racks to cool completely.

TO MAKE THE FROSTING AND ASSEMBLE CAKE:

12. To make the frosting, combine the butter and shortening in a large mixer bowl until smooth.
13. Add about half of the powdered sugar and mix until well combined.
14. Add the vanilla extract, cinnamon and 3-4 tablespoons of water or milk mix until well combined and smooth.
15. Add the remaining powdered sugar and mix until combined.
16. Add additional water or milk as needed to get the right consistency and mix until well combined and smooth.
17. To assemble the cake, use a large serrated knife to remove the domes from the top of the cakes.
18. Place the first layer of cake on a serving plate or a cardboard cake round. Pipe a dam of frosting around the outside of the cake. I use Ateco tip 808 for the dam so that it’s tall.
19. Spread about 1/3 of the pecan pie filling evenly on top of the cake layer, inside the dam, then smooth out the dam of frosting so that it’s all even.
20. Add the second layer of cake and repeat the dam and pecan pie filling.
21. Add the final layer of cake on top, then smooth out the frosting around the sides of the cake.
22. Frost the outside of the cake. Feel free to use my tutorial for frosting a smooth cake.
23. Finish off the cake by piping a border around the top edge of the cake and filling it in with the remaining pecan pie filling. Press pecan halves into the sides of the cake.
24. Refrigerate cake until ready to serve. Cake is best for 2-3 days and best served at room tempe