Whisk the peanut butter, ground ginger, maple syrup, soy sauce, rice wine vinegar, sesame seeds, crushed red pepper flakes and 2 tablespoons of the hot water together in a bowl, a jar with a lid (shake vigorously) or a small blender or food processor until smooth.
Add some of the extra 2 tablespoons of hot water a little at a time to the sauce, whisking it in, depending on whether you need this for a sauce, dip or a dressing, to your desired consistency.
Taste and adjust sweetness or saltiness according to your preference.
This can be made ahead of time and stored in the fridge, or used immediately!
