01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - Beat butter and powdered sugar in large bowl with mixer until light and fluffy, about 2–3 minutes.
03 - Mix in instant espresso powder and vanilla extract until well combined.
04 - Gradually add flour and salt. Mix just until dough comes together.
05 - Fold in toffee bits by hand, distributing evenly throughout dough.
06 - Scoop tablespoon-sized balls onto prepared baking sheets, spacing 2 inches apart. Flatten slightly with hand or glass bottom.
07 - Bake 16–18 minutes until edges are lightly golden.
08 - Cool on baking sheet for 5 minutes, then transfer to wire rack to cool completely.