The first way to make nuts completely nutritious (and delicious!) is to soak them overnight in water and a little sea salt. This neutralizes the phytic acid and breaks down enzyme inhibitors that are naturally present in all forms of seeds (including whole grains, nuts, seeds, and beans/legumes). This is a very important first step, whether you are making a butter from the nuts, or just plan to enjoy them whole as a snack or a salad topping.
I used about 2 cups of shelled, skinless peanut halves, and 2 cups of pecan halves but you could use any type of nut (such as cashews, almonds, brazil nuts, macadamia nuts, or walnuts). [Keep in mind that this makes quite a lot of nut butter, so you may want to halve the recipe the first time you make it if you're not sure you will like the results. I think you will, though!]
First, place the nuts in a bowl and cover with water; add 1 tbsp. sea salt to each bowl (use one soaking bowl for each type of nut to keep them separate) and cover with plastic wrap. Leave the bowls in a warm place for about 12-24 hours.
Next, drain the nuts, spread them on a baking sheet (again keeping the different kinds on separate sheets), and slowly dry them out in a warm oven set no higher than 150 degrees. You can turn them occasionally, but otherwise you don't need to supervise them much. There is no possibility of burning so you can pretty much leave them on their own, just checking every few hours. You will need to bake them in this way for about 7-15 hours until they are completely dry and crisp. I left mine in the oven overnight which was very convenient. You really don't have to worry about them too much as the temperature is set so low; they just need a good amount of time to dry out completely. This picture is of the "crispy" pecans - the soaking and drying really brings out the buttery flavor.