Preheat oven to 350 degrees and line a baking sheet with parchment paper.

Add butter, brown sugar, and sugar to a large bowl. Beat until smooth and creamy.

Add vanilla and egg and beat to combine.

In a separate bowl, whisk together the gluten free baking flour, cornstarch, baking soda, and salt. Add the flour mixture to the sugar mixture and mix until combined.

Fold in the chocolate chips and toffee bits.

Drop dough by ¼ cupfuls onto the prepared baking sheet. Flatten the cookies slightly before baking.

Bake for 14 to 16 minutes, until edges are golden brown but centers are still soft.

Allow to cool on the baking sheet for 5 minutes, then transfer to a wire cooling rack to cool completely.