In a medium-sized bowl, stir together the flour, cornstarch, baking soda, and set aside.
In a large bowl, whisk together the butter and brown sugar until smooth.
Add the egg, vanilla, and butter extract, whisk until combined and smooth.
Add the flour mixture to the bowl and stir it in until combined with no dry patches. This may take a few minutes.
Fold in the pecans.
Line a sheet tray with parchment paper. Using a 1.5 tablespoon cookie scoop, or heaping tablespoon-sized dollops, portion the cookie dough and place them, not touching, but close together on the parchment paper. Cover and place in the refrigerator for two hours, up to overnight.
Preheat the oven to 350°F. Line sheet trays with parchment paper. Take the cookie dough balls and roll them between your hands to form a smooth ball, they will be hard at first but will soften up.
Roll them in the decorators sugar.
Place them on the sheet trays 2 inches apart. Gently press the pecan halves on to the tops of the cookies, if using.
Bake for 9-10 minutes until the cookies are puffed, the tops are not shiny, and they are slightly browned.
Let them cool on the sheet tray for 10 minutes, then transfer the cookies to a wire rack to cool completely.
Notes
Topping with pecans is optional but makes a great presentation and texture contrast.
Do not skip the chilling, this is essential for the cookies to turn out (it keeps them from spreading too much)
If you cannot find butter extract you can use all vanilla.
These can be frozen, see my tips above.
Easily double this recipe to have more on hand, for gatherings, cookie exchanges or to freeze for later.
If you only have unsalted butter, you will need to have 1/2 teaspoon of salt.
Can't find decorators sugar? Just roll in regular sugar.