1. Prepare the streusel filling: In a medium sized bowl combine the flour, brown sugar, cinnamon and salt together. Then work in the butter until small clumps form. Refrigerate.

2. Preheat the oven to 400°F. Line two baking sheets with parchment paper or silicone baking mats. Set aside.

3. Combine the dry ingredients in a large bowl: all purpose flour, cake flour, corn starch, cinnamon, baking soda, baking powder and salt. Set aside.

4. Place the cubed butter and sugars into the bowl of a stand mixer and secure the paddle attachment. Turn the mixer on and cream until smooth, about 1-2 minutes.

5. Add in the egg, egg yolk and vanilla extract and blend until mixed. Scrape down the bowl and mix again.

6. Gradually add in the dry ingredients, about 1/4 cup at a time. Mix until incorporated.

7. Scoop and roll cookie dough into ~8 large balls, or smaller if preferred. Place on prepared baking sheets.

8. Make an indent in each cookie using your thumb or a utensil. Spoon ~1 Tbsp. of the streusel filling in each cookie.

9. Bake for 8–11 minutes, or until edges appear set and are slightly golden.

10. (Optional) To shape the cookies perfectly, use a large circular cutter to swirl around each cookie immediately after baking.

11. Let cookies rest on the baking sheet for 5 minutes then transfer to a cooling rack.

12. Whisk together the ingredients for the icing. Once the cookies are fully cooled, drizzle icing over the tops and enjoy!