Preheat the oven to 350. Add butter, brown sugar, and white sugar to a stand mixer. Mix for 2-3 minutes. Add eggs and vanilla, and mix again.
Add flour, cornstarch, baking soda, and salt. Mix until just combined.
Combine cinnamon and sugar in a small bowl. For Crumbl sized cookies, scoop ½ cup of dough and roll into a ball. Drop the dough into the bowl with cinnamon and sugar and roll to coat the entire ball.
Add up to 6 cookies on a normal sized cookie sheet. Flatten the dough balls slightly. Bake for 9-11 minutes. Cookies should look just set, possibly still slightly doughy. This is perfect. Let the cookies cool completely.
While the cookies cool, make the frosting. Combine butter and cream cheese in a stand mixer and mix for 2 minutes. Add powdered sugar and vanilla and mix another two minutes.
Pipe frosting onto each cookie and dust with extra cinnamon sugar. Enjoy!
