In a mixing bowl, combine all-purpose flour, brown sugar, cinnamon, and a pinch of salt. Cut in the cold unsalted butter using a fork or pastry cutter until the mixture turns crumbly.

In a large bowl, whisk together the all-purpose flour, cake flour, cornstarch, baking soda, baking powder, cinnamon, and salt until well combined.

In a separate bowl, cream the cold unsalted butter and both sugars until light and fluffy, about 3-4 minutes. Then add the egg, egg yolk, and vanilla extract, mixing until smooth.

Gradually incorporate the dry ingredients until just combined, being careful not to overmix.

Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper. Form the cookie dough into balls and place them on the baking sheet about 2 inches apart.

Create an indentation in the center of each cookie, allowing room for the streusel filling.

Bake the Coffee Cake Cookies for 8-11 minutes until edges are set but centers appear slightly underbaked.

Remove from oven and allow to cool for a few minutes on the baking sheet before transferring to a wire rack.

Prepare the glaze by melting unsalted butter and mixing it with powdered sugar, cream, vanilla extract, and a pinch of salt until smooth. Drizzle over cooled cookies and allow to set.