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.

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

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

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.

Add in the egg, egg yolk and vanilla extract and blend until mixed. Use a rubber spatula to knock off mixture if any is sticking to the sides of the bowl and mix again.

Gradually add in the dry ingredients, about ¼ cup at a time. Mix until incorporated.

Scoop and roll cookie dough into ~8 large balls, or smaller if preferred you can get about 22-24 cookies. Place on prepared baking sheets.

Make an indent in each cookie, using your thumb or the end of a spoon/spatula or something similar.

Spoon ~1 Tbsp. of the streusel filling in each cookie and bake for ~8-11 minutes, or until edges appear set and are slightly golden.

Let cookies rest on cookie sheet for ~5 minutes then transfer to a cooling rack.

Whisk together the ingredients for the icing and once the cookies are cooled, drizzle icing over the tops and enjoy!