Heat the butter in a medium pot over medium heat. Add the onion and cook for about 3 minutes. Add the garlic and cook for about 30 seconds more.
Add the chicken broth, lime juice and avocados in the sauce pot and bring to a boil. Reduce the heat to medium and cook for about 7 minutes.
Transfer to the blender and blend until smooth. Return the mixture to the pot. Add the heavy cream, cumin, salt and pepper.
Cook over medium heat for about 5 minutes. Add fresh cilantro and serve warm.
