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