For the Cake:

1. Preheat the oven to 350°F. Prepare three 8-inch round pans, line the bottom with parchment paper, and grease the sides.  Once preheated, toast the pecans on a cookie sheet for 5 to 8 minutes. Cool them and chop them into smaller pieces, set aside.
2. 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.
3. In a large mixing bowl, combine the cake mix, pudding mix, and light brown sugar and stir to combine. Next add the eggs, buttermilk, vegetable oil, sour cream bourbon, and vanilla extract. Start mixing on a low speed until the ingredients start to incorporate. Add the melted butterscotch chips and 1 cup of pecans and mix the batter until all the ingredients are well combined.
4. Divide the batter evenly between the 3 cake pans. 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.

For the Frosting:

1. 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 starts boiling, stir it frequently and it will slowly start to turn an amber color and release a nutty aroma. Remove the butter from the heat and place in a separate bowl to cool. The butter needs to be cooled until it’s a soft solid, and still spreadable. Place in the refrigerator or freezer to speed up the process. 
2. Cut the remaining butter into pieces. Using the paddle attachment, whip the butter for 3-4 minutes, scraping down the bowl occasionally. Beat until the butter looks light in color. Then add in the brown butter, beating until it’s incorporated.
3. Add 4 cups powdered sugar and the vanilla extract and mix on low speed until well incorporated, then increase the speed and beat for another. minutes. Then add another 3 cups of powdered sugar, with the heavy cream (or bourbon), and beat on low speed until incorporated then increase to high speed, beating for 1-2 minutes until the frosting is fluffy and spreadbale. 

To Assemble:

1. Use a cake leveler to cut the domes off the top of the cake. Place a dollop of frosting on your cake board and place the bottom layer of cake on top of that.
2. Place about 2 cups of frosting in a large piping bag fitted with a large open round tip, or simply cut off the end of the piping bag. Using 1 cup of frosting for each layer, pipe a layer of frosting starting at the outside edge and working your way into the middle. Spread evenly with an offset spatula. Place another layer on top and repeat the frosting with the second layer, then place the final layer on top, inverted so the bottom of the cake is on top.
3. Use your piping bag to fill in any gaps between the layers and to create a rough crumb coat. Using an offset spatula, wipe away the excess frosting, leaving 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.
4. Remove the cake from the refrigerator and proceed to finish frosting and decorating. Use the remaining pecans and push into the bottom edge of the cake then drizzle with caramel sauce right before serving.