Preheat oven to 325F and line 2 cookie sheets with parchment paper.
In a medium bowl, toss together the flour, powdered sugar, cornstarch, and salt. Set aside.
2 & 1/4 cups (285g) all-purpose flour, 1/2 cup (60g) icing sugar, 1/4 cup (30g) cornstarch, 1/2 tsp salt
In a large mixing bowl, beat the butter and vanilla until light and fluffy.
1 cup (227g) unsalted butter, 1 tsp vanilla extract
Slowly mix in the dry ingredients until almost combined. Then fold in the toffee bits until just combined. The dough might seem dry and crumbly but it will come together when you roll it in your hands.
1 cup (160g) Skor toffee bits
Scoop the dough using a tablespoon or cookie scoop. Roll the dough into a ball and place 2" apart onto the prepared baking sheets. Flatten slightly with the palm of your hand.
Bake for 15 minutes or just until the bottoms start to brown. Let cool for 10 minutes before serving.
Notes
Leftovers can be stored in an airtight container at room temperature for up to a week.
Troubleshooting:
Cookies not spreading - If the cookies don't spread at all in the oven, that means too much flour was added. Just press and flatten the dough more before putting it in the oven.
Cookies spreading too much - This means the butter was too warm or there was not enough flour is causing the dough to be too soft. Just chill the dough for 15-30 minutes to firm it up before baking.
Cookies are dry - If the cookies turn out dry, then they were overbaked. Just enjoy them with a cup of tea or a glass of milk and bake for a few minutes less next time.
Variations:
You can substitute the Skor candy bits with chopped Toblerone chocolate, mini chocolate chips, chopped pecans or walnuts, or a combination of these add-ins.