Preheat oven to 350 degrees. Use parchment paper or a silpat mat to line a baking sheet.
Cream the butter, brown sugar and granulated sugar in a stand mixer until light and fluffy (about 2-3 minutes). Scrape the sides of the bowl to make sure all ingredients are blended.
Add in the egg and vanilla and beat until combined.
Add in flour, baking powder, salt and baking soda. Mix until all combined.
Stir in the chocolate chips and toffee pieces.
Scoop out 1 TBSP dough for smaller cookies (or 1/4 cup dough for BIG cookies). Place dough balls on prepared pan (12 cookies to a pan if smaller cookies).
Bake for 9-10 minutes. Cool cookies cookie sheet for 10 minutes before removing to cooling rack. NOTE: If you decide to make the bigger cookies, you’ll need to bake them for 13-15 minutes.
Sprinkle with sea salt immediately after removing from oven.