01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - Beat butter and powdered sugar together with electric mixer until light and fluffy, about 2-3 minutes.
03 - Mix in instant espresso powder and vanilla extract until thoroughly combined.
04 - Gradually add flour and salt. Mix just until dough comes together, being careful not to overmix.
05 - Add toffee bits and fold by hand until evenly distributed throughout dough.
06 - Scoop tablespoon-sized dough balls onto prepared baking sheets, spacing 2 inches apart. Flatten each ball slightly with hand or glass bottom.
07 - Bake for 16-18 minutes until edges are lightly golden.
08 - Let cookies rest on baking sheet for 5 minutes, then transfer to wire rack to cool completely.