Start by preheating your oven to 350°F (177°C) and lining your baking sheet with parchment paper.
Then cream together the softened 1 cup unsalted butter, 1 ½ cups brown sugar, and 1 teaspoon vanilla extract.
Stir in the 1 ½ cups all-purpose flour, 1 tablespoon cornstarch, 2 teaspoon baking powder, ½ teaspoon baking soda, 1 teaspoon cinnamon, and ½ teaspoon salt until a gooey dough is formed, then fold in the 2 ½ cups old-fashioned oats.
Use your 2-tablespoon cookie scoop to scoop 6 cookie dough balls onto your parchment lined baking sheet.
Bake for about 11-12 minutes, then let cool for at least 5 minutes on the baking sheet before moving to a cooling rack.
Repeat with the rest of the cookie dough and enjoy when cooled!
Notes
This dough is quite thick, so a sturdy spoon or spatula works better than a whisk, once the dry ingredients go in.I used a 2-tablespoon scoop and got 30 cookies, but you can make the dough balls smaller. Just keep an eye on the baking time: The smaller they are, the quicker they will bake.These cookies are ready to pull from the oven when they’re slightly golden on the bottom. Cookies continue baking when you take the tray out of the oven, so allow them to cool for 5 minutes before transferring them to a wire rack to cool completely.The cookies will seem soft when they come out of the oven. Don’t worry – they’ll firm up as they cool.Store in an airtight container at room temperature for 4-5 days for best results.