These oatmeal chocolate chip cookies are so soft & chewy! An easy recipe that's loaded with lots of melty dark chocolate and hearty oats.
Place the butter, brown sugar, and granulated sugar in a large mixing bowl, and cream together on medium-high speed for a FULL 5 minutes, scraping the bottom and sides of the bowl with a silicone spatula as needed.
Scrape the bottom and sides of the bowl with a silicone spatula, then stir in the egg, egg yolk, and vanilla until incorporated.
Add the flour, oats, cornstarch, baking soda, and salt, and mix together on low speed until just barely combined.
Fold in the chocolate chips, then scoop 1.5-tablespoons of dough at a time onto the prepared baking sheet, allowing about 2 to 3 inches in between (for spreading).
Bake for 7 to 9 minutes, or until just barely beginning to turn golden around the edges (the cookies will still look quite wet towards the centers).
Allow to cool fully on the baking sheet.