For the Cinnamon Roll Cookies:

1. Start by making the cinnamon swirl. Mix the softened butter, brown sugar, flour, and cinnamon in a small bowl until smooth. Line a small plate or baking sheet with parchment, spread the mixture on one half, then fold the paper over it. Press it flat into a thin layer—almost like making a quick cinnamon “bark.” Pop it in the freezer for 10 minutes (or fridge for 20) while you make the cookie dough.
2. Now make your cookie dough. In a large bowl, add the butter, brown sugar, and white sugar, and beat on low with a hand or stand mixer until combined, then increase the speed to medium and beat until light and fluffy, about 2 minutes. Use a silicone spatula to scrape down the sides.
3. Add the egg, egg yolk, and vanilla, and beat on medium high speed until lightened in color, about 1-2 minutes. 
4. In a separate bowl, whisk together the flour, salt, baking soda, and baking powder.
5. Gently fold the dry ingredients into the wet until just a few streaks of flour remain. Remove the cinnamon swirl from the freezer or fridge and remove the parchment paper. Chop into small bite sized pieces and add to the cookie dough. Gently fold until combined. You want to have some cinnamon swirls and some chunks. 
6. Using a 2 tbsp cookie scoop, scoop the dough into balls and add to a parchment paper lined baking sheet. Cover the dough with plastic wrap and refrigerate at least 30 minutes, ideally 1 hour. This helps improve the flavor of the cookies and keeps them from spreading too much. 
7. Preheat the oven to 350°F. 
8. Make the cinnamon sugar coating. In a small bowl, mix together the sugar and cinnamon until combined.
9. Line another baking sheet with parchment paper and roll the cookie dough into smooth balls and toss in the cinnamon sugar to coat. Place on a baking sheet 2-3” apart, baking in batches to not overcrowd the pan. 
10. Bake in a 350°F oven for 8–10 minutes, until the edges look set but the centers still appear soft. You want to pull these when they are slightly underbaked as they will continue cooking as they rest. While cookies are still warm, use the top of a mason jar or cup to round the cookies into a perfect circle.
11. Let the cookies cool on the baking sheet for 5 minutes—they’ll be very soft—then transfer to a wire rack to cool for another 5–10 minutes. 
12. Store baked cookies in an airtight container at room temperature for up to 1 week, or freeze the unbaked dough balls for up to 3 months.