Mal and I modified a sweet Miso-PB sauce (Miso, PB, honey) to make this saltier dip (Miso, PB, tamari). It sounds a little weird at first, but it is truly delicious and addictive. I recommend using natural peanut butter, which is less sweet, but any kind should do in a pinch.
In a bowl, combine:
2/3 cup peanut butter
1/2 cup miso paste
generous splash of tamari sauce
1/2 (or so) hot water
Whisk together to remove any lumps, adding more water if you wish to achieve a smoother consistency. The sauce will become slightly lighter in color.
Refrigerate until it thickens, and serve cold with raw vegetables, on sandwiches, whatever!