Preheat oven to 350 F and coat a 13 x 9-inch baking dish with nonstick spray. Set aside.

Whisk together flour, baking soda and salt in a medium-sized bowl. Set aside.

Beat butter and brown sugar in a large mixer bowl on medium speed until pale and fluffy. Beat in egg and vanilla until combined. Reduce speed to low and gradually add flour mixture. Beat just until flour is incorporated. Fold in chocolate chips and toffee bits.

Scrape batter into the prepared baking dish and use a sheet of parchment to press the dough evenly into the pan. Bake in the preheated oven for 15 minutes, or until edges are golden and a toothpick inserted in the center comes out with a few crumbs attached. Remove from oven to cool completely in pan on top of a wire rack.

Just before cutting it into bars, move pan to the refrigerator and chill for 15 minutes. Then cut into squares with a sharp knife. Store in an airtight container at room temperature up to 3 days.