Cream wet ingredients together - Add softened butter, vanilla, molasses and sugar to a stand mixer bowl fitted with the paddle attachment. Beat on medium speed until the mixture is thoroughly incorporated and creamy.
8 oz unsalted butter, ⅔ cup granulated sugar, 2 tablespoon molasses, 1 teaspoon pure vanilla extract
Add dry ingredients - Sift flour and cornstarch directly into the stand mixer bowl with the creamed butter. Sprinkle in the salt and stir to combine. Increase the mixer speed and beat until no trace of flour remains and the dough is formed.
2 ¼ cup all-purpose flour, 2 tablespoon cornstarch, ¼ teaspoon kosher salt
Form the logs - Place a long piece of plastic wrap flat on the countertop. Divide cookie dough into 2 equal portions. Roll each portion on top of the plastic wrap into a log about 6” in length. You don’t need additional flour for rolling but you can use some flour if necessary.
Add sanding sugar to the outside - Sprinkle 1 tablespoon of raw sugar along the length of the plastic wrap and roll the cookie dough log over it so the sugar sticks all around the outside of the dough log. Wrap it up with the plastic and refrigerate for at least 1 hour before baking. I usually refrigerate shortbread dough overnight to prep ahead.
¼ cup raw sugar
Slice the cookies - Use a sharp knife to slice each cookie dough log into 12 cookies about ½” thick. Rewrap in the same plastic and place them into the freezer while the oven preheats, about 15 minutes.
Preheat the oven - Set the oven rack in the middle of the oven and preheat to 350°F.
Bake - Place 12 cookies on a large lined baking sheet, about 2 inches apart. Sprinkle more raw sugar on top and bake 1 batch at a time for 20 minutes, until the cookies are a deep golden.
¼ cup raw sugar
Cool - Remove the baking sheet from the oven, but allow the cookies to sit on the baking sheet to finish baking from the residual heat for 5-10 minutes before removing them to a wire rack to cool completely.
Notes
Storing baked cookies: store your molasses shortbread cookies in an airtight container at room temp for up to a week.
Storing cookie dough: cookie dough can be kept refrigerated for 3-4 days before baking to prep ahead. Or slice and freeze for 3-6 months.
Baking frozen dough: no need to thaw frozen cookie dough, you can bake directly from the freezer.