Adapted from Eat, Live, Run
First things first, if you do not have your walnuts finely chopped, chop them up in a food processor until very fine and meal-like.
In a large bowl, beat butter on medium high speed for 4 - 5 minutes or until light and fluffy.
Add in the powdered sugar (carefully), soy milk, and bourbon. Beat on low - medium speed until everything is combined.
Finely, beat in the finely chopped walnuts until evenly incorporated.
You are now ready to top your favorite baked good with this delicious concoction!