Step 1

Place 2 sticks Challenge Unsalted Butter in the bowl of a stand mixer (or large bowl if using an electric hand mixer). Let sit at room temperature until softened.

Step 2

Arrange 2 racks to divide the oven into thirds and heat the oven to 350ºF. Meanwhile, line 2 baking sheets with parchment paper or silicone baking mats. Place 1 cup of the powdered sugar and 2 teaspoons of the ground cinnamon in a small bowl and stir to combine.

Step 3

Beat the butter with the paddle attachment on low speed until creamy, 1 to 2 minutes. Add the remaining 1/4 cup powdered sugar, remaining 1 teaspoon ground cinnamon, 1/2 cup granulated sugar, and 1 teaspoon kosher salt. Beat on low speed until just combined, about 1 minute. Stop and scrape down the attachment and sides of the bowl with a flexible spatula.

Step 4

Add 1 large egg yolk and 2 teaspoons vanilla extract, and beat on low speed for 1 minute. Add 2 cups all-purpose flour and beat on the lowest speed just until combined and a soft dough forms, about 1 minute.

Step 5

Scoop the dough out in level 1-tablespoon portions and roll each portion into a ball. Place on the baking sheets, spacing them at least 1 1/2 inches apart, up to 20 per sheet.

Step 6

Bake for 10 minutes. Rotate the baking sheets between racks and from front to back. Bake until the tops of the cookies are dry and the bottoms are light golden brown, 4 to 6 minutes more.

Step 7

Let the cookies cool on the baking sheets for 10 minutes. While still warm, place each cookie in the cinnamon sugar, toss until completely coated, and return to the baking sheets. Reserve the remaining cinnamon sugar. Let cool completely, about 15 minutes more. Coat again in the cinnamon sugar.