Preheat the oven to 350°F. Grease a 9X13 inch glass or ceramic baking pan.
In a bowl, stir together the butter and brown sugar. Add the egg and vanilla. Whisk until smooth.
In a small bowl, mix together the flour, baking powder and 1/2 tsp salt. Add to the butter and sugar mixture.
Fold in the toffee pieces and chocolate chips but reserve 1/2 cup of chocolate chips for later.
Pour the batter into the pan and spread evenly. Bake for 25 to 30 minutes or until top is golden and a toothpick stuck in the center comes out clean.
Melt the remaining 1/2 cup of chocolate chips in a double boiler or microwave oven. Drizzle the melted chocolate over the baked cookie bars. Sprinkle with sea salt. Cool for 20 minutes before cutting into 32 squares.
Keyword Baked, Bar Desserts, Chocolate, Chocolate Chip Cookies, Cookies, Desserts, Party Food