Preheat the oven to 350℉. Line baking sheet(s) with parchment paper.
In a large bowl, using an electric handheld mixer on medium speed, mix the softened butter, brown sugar, and white sugar until combined. Add the egg, egg yolk, vanilla, and peanut butter and beat on high speed until fluffy.
Add the flour, baking soda, cream of tartar, and salt and mix on low speed just until combined. Fold in the chocolate chips.
Roll into balls of 1-2 tablespoons of dough and place the prepared baking sheet, placing each cookie 2 inches apart. Bake in the preheated oven for 6-10 minutes or until puffy and no longer wet-looking on top. Let cool on the baking sheets for 10 minutes before transferring to a wire rack to finish cooling. Finish baking the remaining cookies. Enjoy!
Notes
Or use unsalted butter with ½ teaspoon of extra salt added to the recipe.
You may use creamy or crunchy peanut butter in this recipe, whichever you like best. Do not use natural peanut butter as it is much more runny and oily than regular peanut butter.
You could also use milk chocolate chips if you prefer.