Preheat the oven to 350 F, and position a rack in the center of the oven. Line a baking sheet with non-stick parchment or baking paper.
In a bowl, stir together 1 cup of the sugar with the egg yolks, until moist and crumbly. Stir in the peanut butter to make a dough.
Divide the cookie dough into 12 equal portions. Roll each portion of dough into a ball with your hands, and coat the dough balls in the remaining 1/4 cup sugar.
Use a fork to flatten the dough balls and to make a criss-cross impression on top. Note that since the cookies barely spread while baking, you should flatten them to the thickness that you want the baked cookies to be.To make different patterns on the cookies, you could also use other objects or utensils from your kitchen to flatten the cookie dough. Instead of a fork, try a pastry blender, potato masher, meat tenderizer, cocktail muddler, or a cookie stamp.
Place the cookies on the baking sheet. They don't spread much at all, so they only need about 1 1/2 inches in between. Bake for 9 minutes. The cookies should look set around the edges, but still slightly underdone.
Cool on the baking sheet for 2 minutes, then transfer to a cooling rack to cool completely. If desired, sprinkle the tops of the cookies with flaky finishing salt, such as Maldon.
If using a natural creamy peanut butter that's thin, runny and needs to be stirred (such as Adams 100% natural), reduce the peanut butter by 2 tablespoons. For all other types of peanut butter, including "natural no stir" varieties, follow the recipe as is.If your peanut butter is unsalted, you'll probably also want to add a pinch of salt to the cookie dough, or sprinkle some on top of the baked cookies.