In the bowl of a standing mixer, add all of the cake ingredients except for the walnuts. Beat on medium speed for 5 minutes. Add the walnuts to the bowl and beat for another minute. The batter should be THICK.
Spray your loaf pans with cooking spray before filling each pan halfway up with batter. Bake in your preheated 350-degree oven for 35 to 40 minutes or until a toothpick inserted in the middle comes out clean.
While the cakes are still warm, make the frosting. First, melt the butter in a large bowl and then add the SoCo and powdered sugar. Whisk until the frosting is smooth. Set aside 1 1/2 cups of the frosting in a separate bowl.
Now, back to the freshly baked whiskey cakes. Poke holes all through them and then pour the frosting over the top. Allow the cakes to finish cooling before finishing.
Fold the walnuts into the reserved bowl of frosting. Once the frosted cakes have cooled completely, then you can go ahead and spread a layer of walnut frosting over the top. Enjoy!