2Working with a stand mixer fitted with the paddle attachment, or in a large bowl with a hand mixer, beat the butter, sugar, salt and cinnamon, if you’re using it, together on medium speed for about 3 minutes, scraping down the bowl as needed, until well blended.
3Mix in the vanilla and espresso extract on low speed. Turn off the mixer, add the flour all at once and pulse to begin incorporating it, then mix on low speed until the flour almost disappears into the dough. Scrape down the bowl, add the chopped chocolate and mix until evenly distributed. Give the dough a few last turns with a sturdy flexible spatula.