In a medium-sized bowl, stir together the flour, cornstarch, baking soda, and salt, set aside.

In a large bowl, whisk together the butter and brown sugar until smooth. Add the egg, vanilla, and butter extract, whisk to combine, 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 fridge 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 decorator's sugar and place them on the sheet trays 2 inches apart. Gently press the pecan halves onto the tops of the cookies if using.

Bake for 12-14 minutes until the cookies are puffed, the tops are not shiny, and they are slightly golden brown. Let them cool on the sheet tray for 10 minutes, then transfer the cookies to a wire rack to cool completely.