For the cake: Preheat the oven to 350° F. While the oven is preheating, toast the pecans.
To toast the pecans, sprinkle them on a cookie sheet and toasted for 5 to 8 minutes until you smell the aroma of nuts.
Grease and flour three 8-inch pans. Optional, line the pan with 8-inch parchment paper circles. Trace the outside edge of the pan on a piece of parchment paper and cut it and place on the bottom of the pan.
In a large mixing bowl, combine the cake mix, pudding mix and light brown sugar and stir to combine.
In a small microwave-safe bowl, melt the butterscotch chips in 30 second increments, stirring occasionally, until the chips are melted and smooth. Set aside.
Add to the mixing bowl: eggs, buttermilk, vegetable oil, sour cream bourbon and vanilla extract. Start mixing on a low speed until the ingredients start to incorporate. Then increase the speed to medium high and add the melted butterscotch chips. Mix the batter until all the ingredients are well combined. Lastly, chop and fold in one cup of the toasted pecans into the cake batter.
Divide the batter evenly between the 3 cake pans, spreading evenly over top. Bake at 350°F for 21-25 minutes until the cake is baked through.
To test the cake for doneness, insert a toothpick into the center of the cake. If the toothpick comes out clean, your cake is done. Allow the cakes to cool completely. You may need to run a knife around the edge of the cake to help release them from the pan.
For the frosting: remove 4 sticks of butter of the refrigerator, one stick will be browned and the other 3 will be left to soften.
To brown the butter, use a small saucepan, and cut the butter into pieces. Melt the butter over medium heat and allow it to boil and bubble. Once it’s stops boiling, stir it frequently and it slowly starts to turn an amber color and releases a nutty aroma. Remove the butter from the heat and allow it to cool.
Cut the remaining butter into pieces. Using the paddle attachment, whip the butter for 3-4 minutes, scraping down the bowl occasionally. Beat until butter looks light in color.
Add 4 cups powdered sugar, one cup at a time and mix on low speed until incorporated into butter. Add 1 tablespoon of bourbon and continuing beating.
Next , add 2 cups of powdered sugar and slowly pour the cooled brown butter into the frosting and beat it into the butter until the frosting is completely smooth.
Add the last two cups of powdered sugar followed by 1 tablespoons of heavy cream and a pinch of salt and beat on low speed until the cream is incorporated. Then beat it at a high speed for 1 minute to whip some additional air into the frosting.
To build the cake: Even out the top of the cake by cutting off the dome using a serrated knife.
Place a dollop of frosting on the bottom of the cake plate and place the bottom layer of cake on top. The frosting will help prevent the cake from sliding.
In order to create even layers, I use a piping bag fitted with an open round tip, or simply cut off the end of the piping bag. I also highly suggest to use a lazy Suzan to rotate the cake as you work.
Fill the first layer of frosting by using your piping bag and pipe from the outside edge into the center. Gently spread the frosting with an offset spatula to fill in the gaps.
Place the next layer of cake on top and repeat the above instructions to fill the layer of frosting.
For the top layer of cake, place it inverted, so the bottom of the cake is actually the top, creating a nice and smooth top edge.
Proceed to add your crumb coat by adding a cup of frosting to the top of the cake and gently spread out to the edges and down the sides. Use the leftover frosting in your piping bags to fill in the cracks between the layers.
Using an offset spatula or icing smoother, wipe away the excess frosting, leaving you just enough to coat the outside of the cake. Do not mix your crumb coating frosting back into your icing if it has cake debris in it. Refrigerate the cake for 15-20 minutes to allow the crumb coat to harden.
Remove the cake from the refrigerator and proceed to the remaining frosting to the top and edges of the cake. To get a nice smooth edge, use your offset spatula and icing smoother to wipe away excess frosting.
Use the remaining chopped & toasted pecans and push into the bottom edge of the cake.