In a medium bowl, combine flour, brown sugar, cinnamon, and salt. Use a fork or pastry cutter to incorporate softened butter until small clumps form. Refrigerate for about 30 minutes.

Preheat your oven to 400°F (200°C). Line your baking sheets with parchment paper.

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

In a stand mixer, cream together the cold cubed butter with granulated and brown sugar until light and fluffy. Add the egg, egg yolk, and vanilla extract.

Gradually add the dry ingredient mixture to the butter mixture, mixing on low speed until just combined.

Scoop large balls of dough, about 2 tablespoons each, and create a small indent filled with 1 tablespoon of chilled streusel topping. Bake for 8 to 11 minutes.

Let the cookies cool on the baking sheets for about 5 minutes. Then transfer them to a wire cooling rack.

In a small bowl, whisk together melted butter, heavy cream (or milk), powdered sugar, and vanilla extract until smooth. Drizzle over cooled cookies.