Ina medium bowlwhisk together flour, baking soda and salt. Set aside.
Instructions
Combine butter and sugars in the bowl of a stand mixer. Beat on medium speed until light and fluffy, about 2 minutes. Beat in egg and vanilla extract. Reduce mixer speed to low and gradually incorporate flour mixture, then toffee and chocolate.
Refrigerate dough for 30 minutes (or up to 48 hours). Meanwhile, preheat oven to 375 degrees F. Drop dough by tablespoonfuls onto parchment-lined rimless baking sheets 2? apart. Sprinkle with remaining toffee bits. Bake about 10 minutes, rotating sheet halfway through. Cookies are done when golden and still soft in the middle.