Start by throwing your roasted peanuts into a food processor. Give the food processor a few spins to grind the peanuts down into a semi-fine texture that still has little bits of peanuts left. This is to ensure that the cookies will have a bit of crunch when you bite into them. If you don’t own a stand mixer then you just throw the peanuts into a ziplocked bag and crush the peanuts that way using a dough roller.
Once you have crushed the peanuts into your desired consistency, set them aside. Now in a large mixing bowl, add in your peanut butter, followed by your melted butter and cooking oil.
Then add in your white granulated sugar, followed by your powdered sugar.
Now add in your table salt and the grind peanuts from earlier.
Then sift in your all purpose flour and mix everything together until you no longer see any white flour spots on the dough.
Now take a spoon about the size of a Tbsp and scoop out the dough.
Shape the dough into a round ball by rolling it in the palms of your hand.
Then place each cookie dough onto a baking tray lined with parchment paper about 1-1.5 inches about to prevent the cookies from touching each other when baking. Yes, the cookies will spread and expand slightly when baking.
Now top each cookie with half of a peanut.
Gently press down on the peanut so that it sticks to the cookie dough.
Then prepare an egg wash by whisking 1 egg with a tsp of milk together.
Apply the egg wash evenly all around the cookie making sure to coat the sides as well. The better a job you do of applying the egg wash to the cookies, the prettier they will look when baking.
Finally bake the cookies in a pre-heated oven at 350°F (180°C) for about 20-22 minutes until the cookies are golden brown. They will have a slight crack to them at the top which is the signature look of these cookies so do not be alarmed if you see them cracking away in the oven baking.