In a small saucepan, whisk together the broth, peanut butter, soy sauce, sesame oil, and chili oil. Set the pan over medium heat, bring to a simmer, and let simmer for 5 minutes. Remove from the heat and stir in the cilantro. Let cool to room temperature, then store in a plastic container in the refrigerator for up to 1 week or in the freezer up to 3 months.