Combine your melted (and cooled) butter and sugar in a large bowl and stir until well-combined.
Add egg, egg yolk, and vanilla extract and stir well.
In a separate, medium-sized bowl, whisk together flour, cornstarch, baking soda, baking powder, and salt.
Gradually add dry ingredients to wet and mix until combined.
Cover bowl with plastic wrap and transfer to the refrigerator to chill for at least 45 minutes.
Preheat oven to 350F (175C) and line a cookie sheet with parchment paper (if you don't have parchment paper, bake directly on an ungreased cookie sheet).
Once oven has preheated, remove your chilled cookie dough from the refrigerator and roll dough into approximately 2-Tablespoon-sized scoops. Roll gently to form a ball and roll through granulated sugar until completely coated with sugar.
Place on prepared cookie sheet (space cookies at least 2" apart).
Bake on 350F (175C) for 11-12 minutes. The centers of the cookies may still seem slightly underbaked -- allow cookies to cool completely on cookie sheet to finish cooking there, cookies will be too fragile to move while hot.
*I like to use half dark brown and half light brown sugar, but you can use all light or all dark, whichever you choose the cookies will turn out! Please see the post for more information on dark vs light brown sugar.
Serving: 1cookie | Calories: 245kcal
Brown Sugar Cookies https://sugarspunrun.com/brown-sugar-cookies/ Find more great recipes at SugarSpunRun.com!