In a medium bowl add the all-purpose flour, light brown sugar, unsalted butter, cinnamon and salt.

Using a small fork, gently mix, and press together all the ingredients until well combined. You may need to use your fingers to gently squeeze the crumble mixture together to create larger crumbs to the texture of your crumble.

Refrigerate the crumble until ready to fill the shaped cookie dough before baking the cookies.

Line two large baking sheets with parchment paper and set aside.

To a medium bowl whisk together the all-purpose flour, cake flour, cornstarch, baking powder, baking soda, salt and cinnamon. Set aside.

To a large mixing bowl, beat together, using a handheld mixer on medium speed, the unsalted butter, light brown sugar and granulated sugar for 30 seconds - 1 minute or until light and fluffy.

Add the egg, egg yolk and vanilla extract to the butter mixture and beat again until well combined and the mixture is smooth.

To the bowl of wet ingredients, add the flour mixture and mix again on low speed just until all the dry ingredients are well incorporated. The cookie dough will be thick.

Using a 2 inch sized cookie scoop, scoop out a dough ball and gently roll it in the palm of your hands to shape it into a smooth ball. Place the dough ball onto one of the prepared baking sheets. Repeat with the remaining dough. Be sure to allow an inch, or two, of space between each of the dough balls on the cookie sheet.

Using your thumb, or the bottom of a rounded tablespoon measure spoon, gently flatten the dough as you press an indentation into the center of the rolled dough balls. You may need to dip your thumb, or the bottom of the measuring spoon, into a small amount of all-purpose flour to help keep the dough from sticking. Repeat until all the dough balls have been shaped.

Place 8 of the chilled and shaped cookies onto the second prepared baking sheet. Be sure to allow 2-3 inches between each cookie as they will spread when baked. Fill each of the indentations with a heaping 1 tablespoon of the crumble mixture.

Bake for 9-11 minutes or until the center is set and the edges of the cookies are just lightly browned.

Allow the cookies to cool on the baking sheet for 5-8 minutes before transferring them to a wire rack, on the counter, to cool completely.

Repeat steps 13-15 until all the cookies are baked and cooled completely.

While the cookies are baking and cooling you can make the icing by adding, to a small mixing bowl, the powdered sugar, 1 ½ tablespoons half & half and vanilla extract. Whisk until smooth then add more half & half (1 teaspoon at a time) until desired consistency is reached for your icing drizzle for the tops of your coffee cake cookies. Your icing should be thin and easy to drizzle.

Using a soup spoon, lightly drizzle each of the cooled coffee cake cookies with the icing. You want to still be able to see the crumble mixture on the tops of each of the cookies.

Allow the icing to firm up before plating, or storing, these coffee cake cookies. It should take approximately 30-40 minutes for the icing to firm up completely before being able to stack the cookies.