Crush the walnuts with the back of a spoon until they have been broken into pea-sized pieces. Mix together the peanut and almond butters until smooth and completely combined. Add the peanut flour, oatmeal, milk, stevia, and vanilla extract and stir until a smooth dough forms. It will become very thick so you will eventually have to knead it with your hands. Add the dried cranberries and walnuts and knead into the dough until they're evenly distributed.