1. Grease the sides of three 8 inch cake pans and place a circle of parchment paper in the bottom for easy removal. Preheat oven to 350 degrees.
2. Beat butter and sugar together until light in color and fluffy, about 2-3 minutes.
3. Add vanilla and sour cream and mix until well combined.
4. Add egg whites in two batches, mixing until well combined.
5. Combine dry ingredients in another bowl, then combine BAILEYS™ Coffee Creamers Frosted Vanilla Cookie and water in a separate bowl.
6. Add half of the dry ingredients to the batter and mix until well combined. Add the creamer mixture and mix until well combined. Add remaining dry ingredients and mix until well combined.
7. Divide batter evenly between three cake pans, then bake for 23-25 minutes, or until a toothpick inserted comes out with just a few crumbs.
8. Allow cakes to sit for 2-3 minutes, then remove to wire racks to cool.
9. To make the filling, beat butter until smooth, then add powdered sugar and beat until smooth.
10. Add the sugar cookie crumbs and vanilla extract and mix until smooth.
11. Add the creamer and mix until smooth, then add flour and mix until smooth and all is well combined. Set filling aside.
12. To make the frosting, beat butter and shortening until smooth.
13. Slowly add 3 cups of powdered sugar and beat until smooth.
14. Add creamer and beat until smooth.
15. Add remaining powdered sugar and beat until smooth. If frosting seems too thick, add more creamer in small amounts.
16. To put the cake together, first cut off the domes on top of the cakes.
17. Place the first layer on a cake plate or cardboard cake circle. Spread about 1/2 of the filling evenly on top of the cake layer.
18. Place second layer of cake on top of the filling and top with remaining filling, spreading into an even layer.
19. Top cake with final cake layer.
20. Cover the outside of the cake with the frosting. Here is a tutorial on how to get a nice smooth finish.
21. Pipe icing around the edges of the cake and add some sprinkles. I used icing tip Ateco 844, which is similar to Wilton 1M.
22. To add the cookies to the outside of the cake, pipe a little remaining frosting onto the backs of the cookies and press them onto the cake.