Combine the dry ingredients (flour, baking soda, salt, corn starch) and sift together.
Melt the butter in a small skillet over medium heat. The butter will start to foam and then start browning. You will be able to smell a nutty aroma when it's ready. Remove from heat and allow to cool slightly. Do not burn!
Cream butter with sugars together in a large mixing bowl.
Beat in the vanilla and then add in the egg and egg yolk and continue beating until the mixture is light and creamy.
Add in the dry ingredients and mix just until combined.
Stir in the chocolate chips and toffee bits.
Put the dough in the refrigerator for an hour to chill.
Preheat oven to 325 degrees.
Drop cookie dough 1/4 cup at a time onto a parchment lined baking sheet.
Space cookies about 3 inches apart and bake for 15 to 17 minutes.
The cookies are done when the edges are golden. Let the cookies cool on the baking sheet for a few minutes and then transfer to a wire racks to finish cooling.