1-Beat softened butter for about 30 seconds until creamy to create a solid base.

2-Add 1 cup (200 g) light brown sugar and ½ cup (100 g) granulated sugar; beat until light and fluffy, scraping bowl sides as needed.

3-Add 2 large eggs one at a time, mixing well after each to ensure even incorporation.

4-Stir in 1 ½ teaspoon vanilla extract for that extra flavor boost.

5-In a separate bowl, whisk together 1 ¾ cup (215 g) all-purpose flour, 2 teaspoons cornstarch, 1 teaspoon baking soda, ¾ teaspoon table salt, and ¾ teaspoon ground cinnamon.

6-Gradually add the dry ingredients to the butter mixture, mixing until combined and scraping the bowl as needed.

7-Stir in 3 cups (285 g) old-fashioned rolled oats until evenly distributed, then add optional mix-ins like 1 ½ cups chocolate chips, chopped nuts, or raisins.

8-Cover the dough with plastic wrap and chill in the refrigerator for at least 30 minutes, or up to 3 days, to enhance flavor and prevent spreading.

9-Preheat your oven to 375°F (190°C) and line baking sheets with parchment paper for easy cleanup.

10-Drop dough by rounded 2-tablespoon balls, spaced at least 2 inches apart, and roll into smooth balls for uniformity.

11-Bake for 10-12 minutes; the edges should be slightly golden while the centers may look underbaked but will set as they cool.

12-Cool cookies completely on the baking sheet before removing or serving to maintain their shape and chewiness.