1. Preheat the oven to 350°F (176°C). Line the bottom of three 8 inch cake pans with parchment paper and grease the sides.
2. In a large mixing bowl, combine the flour, sugar, cocoa powder, baking powder and salt.
3. Combine wet ingredients in another medium sized bowl, then add to the dry ingredients and beat on medium-low speed until well combined. The batter is thin, so be careful of splashing.
4. Divide batter evenly between the cake pans.
5. Bake for 23-26 minutes, or until a toothpick inserted in the middle comes out with a few crumbs.
6. Remove cakes from the oven and allow to cool for 3-4 minutes, then remove from pans to a cooling rack to finish cooling.
7. To make the frosting, beat the butter and shortening until smooth.
8. Slowly add about half of the powdered sugar and beat until smooth.
9. Add cinnamon, maple extract and 3 tablespoons of water or milk and beat until smooth.
10. Add the remaining powdered sugar and mix until smooth.
11. Add additional water or milk a tablespoon at a time as needed to get the right frosting consistency.
12. To make the toffee sauce, melt the butter and sugar over medium heat in a large saucepan.
13. Slowly bring mixture to a boil allowing the sugar to dissolve, about 10-15 minutes.
14. Once it begins to boil, slowly add the heavy whipping cream and bourbon, whisking constantly. The mixture will be bubbly.
15. Whisk for 2-3 minutes, allowing it to come back to a boil. Once boiling, stop whisking and let it boil for 1 minute.
16. Remove from heat and whisk until smooth. Add the flour and whisk until smooth. Set aside to cool a bit.
17. To put the cake together, use a large serrated knife to remove the domes from the top of the cakes.
18. Place the first layer of cake on your serving plate or a cardboard cake circle. Spread 5-6 tbsp of toffee sauce evenly onto the cake layer. It should soak into the cake a bit.
19. Pipe 1 cup of frosting into an even layer on top of the toffee sauce, starting along the outside edge and spiraling inward. With the toffee sauce on top of the cake, spreading will be tough, so piping works best.
20. Sprinkle 2 tablespoons of toffee bits evenly over the frosting. Repeat process with the second layer of cake, toffee sauce, frosting and toffee bits, then add the final layer of cake on top.
21. Frost the outside of the cake with the remaining frosting, then press toffee bits into the sides of the bottom of the cake.
22. Pipe swirls of frosting around the top edge of the cake, then drizzle toffee sauce sauce the sides and fill in the center with more toffee sauce. Sprinkle with some additional toffee bits.
23. Refrigerate cake until ready to serve. Cake is best served at room temperature and is best for 2-3 days when well covered.