First, bake the flour. Preheat the oven to 350° F (180° C) and cover a baking sheet with parchment paper. Spread the 1 cup flour over the sheet to make a thin layer. When the oven comes to temperature, bake the flour for around 12 minutes. The flour will dry out and form some lumps, but you can get rid of these by sifting the flour into the other ingredients.
Using an electric mixer, cream together the butter, peanut butter, brown and white sugars, salt and vanilla. Once they are fully combined, add the milk and mix again.
Sift the flour into the cookie dough and mix until it is fully incorporated.
Stir in the add-ins with a spoon. Serve immediately, or store in the refrigerator for up to 3-4 days.
