Warm peanut butter to soften it (15 seconds in the microwave). Add all other ingredients, stirring to combine. Bring to a boil over low heat, or in 20 second intervals in the microwave, stirring frequently, until thickened and smooth. Taste, and adjust seasoning to suit your palate. If sauce appears to thin, add more peanut butter. If it appears to thick, add more broth.