Using an electric or stand mixer, cream the Finlandia butter until soft. Add both sugars, espresso powder, salt, and vanilla extract, then beat until light and fluffy, about 2-3 minutes. Add flour and mix on low until just incorporated, then mix in chocolate. Do not overmix.
Place the dough on a large piece of plastic wrap and form it into a log about 3 inches in diame-ter. Wrap tightly, then chill for at least 2 hours. Dough can be made up until this point and 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 1/2-inch rounds, then place them on the pans about an inch apart. Bake until they just start to turn golden around the edges, about 15-20 minutes.
Store leftover cookies in an airtight container at room temperature for up to a week.
Makes about 35 cookies.