Cream the butter in a standing mixer, and add brown sugar. Continue to cream until light and fluffy; about 30 seconds. Add both eggs. Mix until well incorporated, and then add vanilla, baking soda, and salt. Give it anther good mix, and then add the flour. Mix until well incorporated, about 30 more seconds.
Using a 4-tsp cookie scoop, spoon cookie dough into balls and roll in granulated sugar. Place dough balls onto a nonstick baking sheet and refrigerate for 30 minutes. Remove from refrigerator and bake at 375° for 12-14 minutes.
Cool cookies on cookie sheet for five minutes, then transfer to a baking rack to cool completely.
As soon as the cookies come out, place walnuts on a shallow baking pan and toast at 375° for 7 to 9 minutes, or until slightly golden and aromatic. Remove and allow to coo. Toss in small bowl with granulated sugar.
Place ingredients for frosting in a small bowl and whisk until fully blended, about 30 seconds. Alternatively you can use a hand mixer as well. Pipe or spread frosting onto completely cold cookies. Top with cooled toasted walnut mixture. Store in an airtight container at room temperature for up to four days. Enjoy!