WET INGREDIENTS: Place the butter in a large bowl and melt in the microwave. Set the bowl aside to cool to room temperature. If the butter/bowl is warm or hot, it will melt the sugars and cause greasy cookies. Once completely cool, add in the white sugar and brown sugar. Whisk together briskly until creamy. Add in 1 whole egg and 1 egg yolk (reserve the whites for a separate recipe or discard) and the vanilla extract. Whisk until just combined and smooth.
DRY INGREDIENTS: In another bowl, stir together the flour, cornstarch, salt, baking soda, and 1 teaspoon ground cinnamon. Whisk together.
DOUGH: Add all of the dry ingredients into the wet ingredients and, using a strong wooden spoon, mix until JUST combined. Do not over mix the dough. Roll balls of dough that are 1 and 1/2 tablespoons in size. Roll the balls tall instead of wide (see pictures in post; See Note 2). In a small bowl, stir together the white sugar and cinnamon. Roll the balls of dough generously into the cinnamon-sugar mixture. Reserve the rest of the cinnamon-sugar mixture for later.
CHILL DOUGH: Place dough balls on a parchment or Silpat-lined sheet pan or plate and chill for 1 hour.
BAKE: Preheat the oven to 325 degrees F (162°C) Place 6 cookies at a time on a parchment or Silpat-lined sheet pan (they need a good amount of room) and bake straight from the fridge for 9-11 minutes. Gently remove from the oven so they don't deflate, let stand on cookie sheet for 5 minutes and then gently remove to a cooling rack.
FROSTING: Meanwhile, prepare the frosting. In a large bowl, beat the room-temperature butter and cream cheese until completely smooth. mix in the vanilla and salt. Add in the powdered sugar and then beat until the frosting is smooth (it will seem like you need more liquid, but just keep beating; it will come together!
FROST COOKIES: Transfer the frosting to a plastic bag or piping bag and cut off the tip. Frost each cooled cookie by piping the frosting in a swirl on top. Sprinkle tops of the cookies with leftover cinnamon sugar mixture.