In a blender or food processor, combine the chiles, lemongrass, garlic, ginger, shallot and 1/4 cup water and puree until smooth. In a large saucepan, heat the coconut oil. Add the lemongrass puree and cook over medium high heat, stirring, until fragrant, about two minutes. Whisk in the coconut milk, muscavado, tamari, peanut butter, lime zest and a cup of water. Simmer over low heat for about 15 minutes.