Beat egg whites until stuff peaks form, and then 1 TBSP at a time, add sugar into the mixer while it is running. After the sugar is completely incorporated into the egg whites, add in your vanilla.
Using a wooden spoon, very gently mix in the toffee and chocolate chips.
Spoon tablespoons of the mixture onto a parchment lined cookie sheet. Place in a preheated oven at 350 degrees, and then turn OFF the oven. Leave the cookies, undisturbed, overnight. Don't peek!!
Remove cookies in the morning and place in a large baggies or other air tight container.