In a bowl, mix flour, brown sugar, cinnamon, and salt for the streusel. Work in butter until clumps form, then refrigerate.

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

In another bowl, whisk all-purpose flour, cake flour, cornstarch, cinnamon, baking soda, baking powder, and salt.

In a stand mixer, cream cold butter with brown sugar and granulated sugar for 1–2 minutes until smooth.

Add egg, egg yolk, and Vanilla Extract (Alcohol-Free). Mix well, scraping sides as needed.

Gradually add dry ingredients, ¼ cup at a time, until incorporated. Do not overmix.

Scoop dough into 8 large balls (or smaller if preferred) and place on baking sheets.

Press a small indent into each cookie using your thumb or the end of a utensil dipped in flour.

Fill each indent with about 1 tablespoon of chilled streusel.

Bake for 8–11 minutes, until edges are lightly golden. Remove just before fully baked to keep soft centers.

Optionally, swirl a round cutter around each cookie to perfect the shape.

Cool on the pan for 5 minutes, then transfer to a wire rack.

For the icing, whisk melted butter, milk, powdered sugar, Vanilla Extract (Alcohol-Free), and salt until smooth.

Once cookies are cool, drizzle icing over each one and let set before serving.