In a medium bowl, whisk together flour, baking powder, salt, and cinnamon. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment, cream butter on medium until smooth and glossy. With the mixer on medium speed, slowly add sugar, and continue to beat until pale and fluffy, 3 to 5 minutes.

Add eggs, one at a time, waiting until the egg is completely incorporated before adding the next. Add vanilla extract, and beat on medium for at least 5 minutes.

Add flour mixture in three additions, mixing on low until the flour is just incorporated. Cover dough and refrigerate until completely chilled, 2-4 hours.

Meanwhile, mark two pencil lines on waxed paper 6 inches apart. Turn paper over and tape to a clean work surface.

Preheat oven to 350°F. Line two baking sheets with silicone baking mats or baking parchment.

Whisk together egg and vanilla extract.

Scoop out a rounded teaspoon of dough, and, working rapidly, place on waxed paper. Using the lines as a guide, roll into a rope 6 inches long. Fold in half, twist 2 times, and place on prepared sheets, leaving about 1 1/2 inches between cookies.

Brush cookies with egg and sprinkle with sesame seeds.

Bake, rotating sheets front to back and top to bottom halfway through, until golden brown, about 22 minutes.

Let cool on sheets fro 5 minutes, then remove from baking sheets to cool completely.