In the bowl of a stand mixer or in a large bowl, mix butter and sugar until the mixture is creamy.
Add 2 tsp Vanilla to the butter mixture.
Mix in 3 cups flour and finally ½ cup chopped pecans.
Roll dough into 1" balls and place on a parchment covered cookie sheet. With your thumb or the back of a spoon press flatten the top of each cookie.
Bake for 10 - 12 minutes.
Cool cookies completely before piping on the icing.
Buttercream Icing
Beat 1 cup butter and 2 tsp vanilla until smooth.
Gradually add in 4 cups powdered sugar, starting at a low speed working your way to a medium. Continue at medium speed for one to two minutes until everything is well combined.
Scrape the sides of the bowl several times while the ingredients mix.
Add 3-4 Tbsp heavy whipping cream (half & half or milk will work) until you have the consistency you prefer. You want the icing to be stiff and cold before piping onto the cookies.
Notes
These cookies do not spread so they can be placed relatively close to one another.