Preheat oven to 375°F. Line two cookie sheets with parchment paper
Make the topping: Combine the granulated sugar and cinnamon together in a small bowl. Set aside.
In a medium bowl, measure all dry ingredients. Set aside.
In a large bowl, using a hand mixer to beat the butter and granulated sugar together until smooth.
Add the egg, egg yolk, and vanilla extract. Beat until combined.
With the mixer running on low speed, slowly add the dry ingredients to the wet ingredients in 3 different parts. The dough will be thick.
Cut the dough into two even balls. Roll a ball into a 12″ log and cut into 12 even segments (1″ each), or about 40g each
Roll each segment into a ball. Coat in cinnamon-sugar topping. Arrange 3 inches apart on the baking sheet.
Prepare second ball while first bakes.
Bake cookies for 10 minutes. The cookies will be very puffy and soft.
Allow cookies to cool on the baking sheet for 10 minutes and transfer to a wire rack to cool completely.
Cookies remain soft & fresh for 7 days in an airtight container at room temperature.
