In a large mixing bowl, using a hand mixer, cream the butter, brown sugar, and ⅓ cup of granulated sugar together until fluffy, about 3 minutes.
1 cup unsalted butter, 1 cup brown sugar, 9 tablespoons granulated sugar
Mix in the eggs and vanilla until combined.
2 large eggs, 2 teaspoons pure vanilla extract
In a separate bowl, whisk the flour, ½ tablespoon cinnamon, baking soda, cornstarch, and salt together.
2¾ cups all-purpose flour, 1 tablespoon ground cinnamon, 1 teaspoon baking soda, 1 teaspoon cornstarch, ½ teaspoon kosher salt
Beat the dry ingredients into the wet ingredients just until combined and dough starts to come together. Do not overmix.
In a separate small bowl, stir together the remaining ¼ cup granulated sugar and ½ tablespoon cinnamon.
Line a baking sheet with parchment paper.
Using a 2-tablespoon-sized cookie scoop, scoop cookie dough batter and drop each raw cookie (one at a time) into the cinnamon-sugar mixture. Roll cookie dough ball around until fully coated in cinnamon sugar then use hands to shape into smooth round balls (do not flatten). Place each cookie onto the lined baking sheet. They can stay close together (but not touching) until ready to bake.
Place raw cookies into freezer for 10 minutes. This step is important for getting nice, fluffy/thick baked cookies.
While the cookies chill, preheat oven to 350°F and line a second baking sheet with parchment paper.
Remove some of the cookies from the freezer and place on the prepared baking sheet with cookies about 2 inches apart from each other. Only bake one tray of cookies at a time.
Bake cookies for 12-14 minutes, or until bottoms of cookies are set. Tops of cookies will not look set yet and that’s okay – they’ll finish baking on the hot tray when you remove them from the oven. It’s normal for these cookies to fall a bit once they’re cooling and out of the oven.
Let the cookies cool on the baking sheet completely before enjoying.