Preheat the oven to 350°F. Line a baking sheet with parchment paper or a Silpat.

In a large bowl or stand mixer fitted with a paddle, add the butter. Beat on medium until creamy and smooth, about 1 minute.

Add the brown sugar, powdered sugar, and vanilla. Beat 1–2 minutes more until light and fluffy. Scrape the bowl.

Spoon 1 3/4 cups + 2 tablespoons flour into a measuring cup and level it off; add this to the butter mixture.

Add the cornstarch and salt. Mix on low just until the dough barely comes together. Avoid overmixing.

Turn the dough onto plastic wrap. Press it into a flat square about 1 inch thick. Wrap tightly and chill for 30–45 minutes.

Lightly flour your work surface. Roll the dough to about 3/8-inch thickness. Cut rounds or fingers.

Optionally, roll each piece in granulated sugar for sparkle.

Place cookies about 1 inch apart on the prepared sheet and freeze the sheet of cookies for 15 minutes.

Bake at 350°F. If baking from frozen, start checking at 11 minutes. Bake until the cookies are set but not browned, approximately 11–14 minutes depending on size.

Remove from oven and gently reshape warm cookies if needed. Transfer to a rack to cool completely.