Using an electric or stand mixer, cream the butter until soft.
Add the granulated sugar, brown sugar, espresso powder, salt, and vanilla extract, then beat on medium speed until light and fluffy, about 2-3 minutes.
Add the flour and mix on low speed until it's just barely incorporated, then mix in chocolate. Do not overmix.
Scrape the dough on to a large piece of plastic wrap and form it into a log about 3 inches in diameter. Wrap tightly, then chill for at least 2 hours. (Dough can be stored in the refrigerator for up to 5 days or in the freezer for up to 2 months.)
Preheat the oven to 325 degrees and line two sheet pans with parchment paper.
Slice the cookies into ½-inch rounds, then place them on the pans about one inch apart.
Bake until they just start to turn golden around the edges, about 16-18 minutes.
Allow the cookies to cool completely on the baking sheet. Store them in an airtight container at room temperature for up to a week.
Video
Notes
*These cookies turn out best when made with a European butter with at least 82% butterfat, and even better if the butter is cultured. If using salted butter, omit the added salt.