Preheat oven to 400° F and line 3 baking sheets with parchment paper.
Cut cold butter into ¼ inch cubes and place in standing mixer, along with brown and cane sugars. Mix for 4-5 minutes, gradually increasing speed to high until dough-like, and no chunks of butter left. You may need to scrape down the sides halfway through.
1 cup unsalted butter, 1 cup light brown sugar, ¾ cup granulated sugar
Using a food processor or blender, grind the oats to your desired consistency.* In another bowl, whisk together flour, ground oats, cinnamon, salt, baking soda, and cornstarch. Set aside.
1 cup old fashioned oats, 2 ¼ cup all purpose flour, ¾ teaspoon ground cinnamon, 1 teaspoon fine sea salt, 1 teaspoon baking soda, 2 teaspoon cornstarch
After the butter and sugar are done mixing, add vanilla extract, eggs, and lemon juice and mix on medium speed until creamy. Scrape down the sides halfway through.
1 tablespoon vanilla extract, 2 large eggs, 1 teaspoon fresh lemon juice
Add flour mixture to the standing mixer and mix on the lowest setting until just combined. Add 2 cups of chocolate chips while the dry ingredients are still mixing in. Don't overmix.
2 ½ cup semi-sweet chocolate chips
Roll the cookie dough into 15 individual balls, and place them spread apart evenly on the baking sheets. Use the remaining ½ cup of chocolate chips and press them into the top of each ball of cookie dough.
Bake for about 9-12 minutes on the middle rack, until tops of cookies start to turn a light golden-brown. Don't overcook! They likely need less time than you think. Immediately out of the oven, you can round out the corners of the cookies with a round cookie cutter or a spoon, if you want the cookies perfectly round.
Let the cookies sit on the baking sheets for at least 15 minutes after baking--this helps the center to cook through and the cookie to solidify (so it doesn't completely fall apart when you pick it up).Enjoy!