Preheat the oven to 350°F.
Line a cookie sheet with parchment paper.
In a medium-sized mixing bowl, whisk together the flour and cornstarch. Set aside.
Using a stand mixer, or a medium size mixing bowl and a handheld electric mixer, cream the butter on medium-high speed for 3 to 4 minutes or until the butter turns a pale yellow. Using a spatula, scrape down the sides of the bowl.
Reduce the mixer speed to low. Slowly add the powdered sugar a ¼ cup at a time, mixing well until the butter mixture is fluffy. Scrape down the sides of the bowl.
Keeping the mixer on low speed, add the vanilla and mix for a few seconds to make sure the vanilla is mixed in well.
Continue to keep the mixer on low speed. Slowly add the flour mixture a ½ cup at a time, mixing well after each ½ cup just until the flour is incorporated.
Add the finely chopped pecans and mix just until the pecans are evenly mixed into the dough.
Using a medium size bowl, add the extra 2 cups of powdered sugar for rolling the warm cookie balls in, and set aside.
Using a 1 tablespoon cookie dough scoop or a tablespoon, scoop out the dough. Carefully but tightly, press and roll the dough in your hands to form the rounded cookie ball. The cookie balls should be about the size of a large marble. Place the cookie dough balls 2 inches apart.
Place snowball dough balls in the refrigerator for 10 minutes, uncovered to chill.
Bake for 10 minutes or until the bottoms are light golden brown.
Remove the cookies and allow them to rest a few minutes until they are easy to handle. Carefully transfer the cookie ball to the powdered sugar bowl. Gently roll the cookies in the powdered sugar. Best to use a fork to move them around in the powdered sugar so the heat from your fingers doesn’t start melting the sugar and making it mushy. Transfer the dusted cookies to a tray to finish cooling completely for a few minutes. Roll the cookies one more time in the powdered sugar to ensure they are completely coated. Store the coated and cooled cookies in an airtight container.