Roast the jalapeños and poblanos under a broiler (or over a gas flame on your stovetop) for about five minutes per side, or until completely blackened. Wrap the poblanos in foil or place in a bag to steam until cool enough to handle. Meanwhile, remove stems from the jalapeños and dice, discarding or keeping seeds depending on spice preference. Once the poblanos are cool enough to touch, remove the stems and peel the skin before dicing.

Melt the butter in a large saucepan set over medium heat. Add onions and cook for 8-10 minutes, until just beginning to brown. Add garlic and cook another minute. Add the peppers, potatoes, broth, cilantro, cumin, and salt and pepper.

Bring to a full boil then reduce heat to low and simmer for about 20 minutes, until the potatoes are tender.

Scoop out 2 cups of the soup and set aside. Remove the pot from the heat, then use an immersion blender to puree the rest of the soup. Alternately, you can work in batches and do this in a blender or food processor. Add the reserved soup back to the pot, along with the milk, cream and black beans.

Heat the soup over medium heat until it comes back to serving temperature. Top with cheese and cilantro.