Preheat oven to 350 degrees F. Have ready two ungreased baking sheets.
Whisk together the flour, baking soda and salt.
In a large mixing bowl, beat the softened butter and brown sugar until creamy. Add the egg and beat until well blended, then beat in the vanilla extract.
Stir the flour mixture into the butter mixture until blended, then stir in the toffee and pecans.
Using a small cookie scoop or rounded teaspoons, scoop out rounds and arrange 2 inches apart on baking sheets.
Bake one sheet at a time for 12 minutes or until cookies appear one.
Alternatively, scoop all of your balls of dough onto a plastic wrap lined tray. Cover and chill several hours or overnight, then bake the chilled dough balls.
You can also make the cookies bigger if you like. A medium size cookie scoop will give you about 20 cookies.