In a mixing bowl, combine peanut butter and soy sauce.
Add rice vinegar and honey (or maple syrup) to the bowl.
Incorporate sesame oil, minced garlic, and grated ginger.
Mix the ingredients until smooth and well blended.
Gradually add warm water, stirring until desired consistency is achieved.
If using, stir in red pepper flakes for a spicy kick.
Taste and adjust seasoning if needed.
Transfer the sauce to a serving dish or jar.
Garnish with fresh cilantro before serving.
Store any leftovers in an airtight container in the fridge.