In the bowl of a stand mixer (or large bowl and hand mixer), combine the butter, sugar, orange zest, cinnamon and Kosher salt. Mix on high speed until light and fluffy.

Add the egg yolks and beat until light and fluffy on high speed.

Reduce the speed to low, add the flour and chocolate chips and mix just until incorporated.

Turn the dough out onto a lightly floured work surface. Divide in half. Roll each piece between your palms and the work surface to form a log 1-inch in diameter.

Wrap the logs tightly in plastic wrap and refrigerate until firm, about 1 hour or as long as overnight.

Preheat the oven to 350°F. Line baking sheet(s) with parchment paper.

Unwrap the dough and cut each log into 1/4-inch thick rounds. Transfer to the prepared baking sheets, spacing 1-1/2 inches apart.

Bake until the edges are brown, about 12-16 minutes.

While the cookies are baking, prepare the cinnamon sugar. Stir together the sugar and cinnamon in a small bowl.

Transfer the cookies to wire racks and let cool for 5 minutes.

Add 1 to 2 warm cookies to the cinnamon sugar bowl. Toss to coat with sugar. Return the cookies to the racks to cool completely. Repeat with the remaining cookies.