01 - Preheat the oven to 350°F. Line two baking sheets with parchment paper.
02 - In a medium bowl, whisk together flour, salt, and espresso powder until evenly distributed.
03 - In a large bowl, beat softened butter and powdered sugar with electric mixer until light and fluffy, about 2-3 minutes.
04 - Mix in vanilla extract until fully incorporated.
05 - Add flour mixture to butter mixture in two additions, mixing on low speed until just combined. Do not overmix.
06 - Turn dough onto lightly floured surface. Shape into rectangle about 1/2 inch thick.
07 - Cut into desired shapes (squares or rectangles) or use cookie cutter. Arrange on prepared baking sheets, spacing 1 inch apart.
08 - Bake for 16-18 minutes, until edges are just starting to turn golden.
09 - Cool completely on wire rack.
10 - If desired, drizzle or dip cooled cookies in melted dark chocolate and sprinkle with flaky sea salt. Allow chocolate to set before serving.