Preheat the oven to 350°F. Line three baking sheets with parchment paper and set aside.
In a medium-sized mixing bowl, whisk the flour, salt, baking soda, cornstarch, and cinnamon (if using).
In a large mixing bowl, add the butter, cookie butter, sugar and brown sugar. Beat until light and fluffy, 1-2 minutes. Add the milk and vanilla and beat again until smooth and creamy.
Add about half of the flour mixture to the wet mixture and mix until just combined. Add the rest and mix until just combined.
Place the granulated sugar in a small bowl.
Roll out ~1.5 tbsp (22 g) balls of dough and roll in the sugar. Place on the prepared baking sheets, leaving about 2" (5 cm) between each.
Bake in the preheated oven for 9-11 minutes. They may look slightly underbaked, but will set while cooling - you don't want to overbake them.
Allow to cool on the baking sheets then enjoy!