To a stand mixer fitted with a paddle attachment add the butter, brown sugar and granulated sugar. Cream together on medium low until light and fluffy, about 3-4 minutes. Scrape down the sides as needed.
Next with the mixer on low add the whole egg plus egg yolk along with the vanilla. Scrape down the sides.
In a medium bowl whisk together the flour, cornstarch, baking soda, baking powder and sea salt. With the mixer on low, slowly add in the flour mixture and mix until you no longer see any flour bits, about 1 minute.
Stir in the peanut butter chips by hand.
Cover the bowl with plastic and place the dough in the fridge, overnight up to 48 hours.
When ready to bake, preheat oven to 350℉. Line a large baking sheet with parchment paper.
Using a small, 1 tbsp. ice cream or portion scoop, scoop the dough onto the lined baking sheet leaving a 1-inch border around the cookies, about 12-13 cookies per tray. Top each cookie with 2-3 extra peanut butter chips. If you want larger cookies use a 3 tbsp. ice cream or potion scoop and leave a 2-inch border around the cookies.
Bake for 8-9 minutes or until puffed, set and golden around the edges, 10-12 minutes for larger cookies. Let cool slightly on the sheet tray before removing to a cooling rack and letting cool fully. Continue with remaining dough. Makes about 72-73 mini cookies or 23-24 large cookies.
To freeze extra dough: portion out the dough with the cookie scoop, dot each one with 2-3 extra chips and place onto a sheet tray. Freeze until hard then remove from the tray and place into a large freezer bag. When ready to bake place directly on the prepared tray and bake for 10-12 minutes.