Whisk together the flour, cinnamon, and salt. Set aside.
Using an electric mixer on medium speed, beat the butter, confectioners’ sugar, brown sugar, and vanilla until thoroughly combined.
Reduce the mixer speed to low. Gradually add the flour mixture, mixing just until combined. The dough will be crumbly but should hold together when pinched. Stir in the toffee bits and pecans.
Chill the dough for 30 minutes. (This will keep the cookies from spreading, but you can skip this step if you’re short on time.)
Preheat the oven to 350°F (175°C). Line baking sheets with parchment paper or silicone liners.
Using a tablespoon of dough at a time, roll the dough into balls. Place on the prepared pans, leaving about 2 inches between the cookies.
Bake for 12 to 15 minutes, or until lightly browned. Cool the cookies on the pans for about 10 minutes. Then transfer the cookies to a wire rack to cool completely. Sprinkle the tops of the cookies with confectioners’ sugar.
Notes
As with all shortbread-like cookies, accurate measurements are very important to make a dough that will hold together well. Please measure by weight if at all possible for the best results. If your dough isn't holding together well, continue mixing (either with a mixer or your hands) until it's more cohesive.