10 kit kat single candies (90 grams), plus 5 extra for garnish (45 grams)
Method
In a small bowl, whisk together the dry ingredients: flour, baking soda and salt. Set aside.
In a medium bowl, add the softened butter, sugar and brown sugar. Beat with an electric mixer on HIGH until super light and fluffy, about 2-3 minutes.
Add the egg and vanilla to the butter-sugar mixture and beat to combine.
Add the dry ingredients to the bowl, and beat just to combine.
Unwrap and chop 10 of the KitKats (90 grams worth) into 3/4-inch pieces, and stir them into the dough.
Refrigerate the dough for 30 minutes. Meanwhile, preheat the oven to 350.
Press the dough flat in the bowl, and divide it in quarters by eye. Try to get 3 cookies out of each quarter, for a total of 12 cookies.
Space the cookies evenly on a baking sheet. Chop up the additional 5 mini Kit Kats (45 grams worth). Press another piece of KitKat into the surface of the dough, and save the remaining pieces for after baking.
Bake the cookies on the center rack for 6 minutes, rotate the pan and bake another 5 minutes. They should be just starting to turn golden brown around the edges, and they will be slightly puffy.
Immediately when the cookies come out of the oven, press extra pieces of KitKat into the dough. I also like to crush a few and sprinkle the crumbs on top because it looks pretty.
Let the cookies cool on the baking sheet for a few minutes, and then move to a cooling rack to cool completely and serve.
