Roast the poblano peppers in the oven at 400°F for 20-25 minutes, turning halfway through. Alternatively, roast over a gas flame or under a broiler for 10-15 minutes until charred.
Cover the roasted peppers with plastic wrap and let them steam for 10 minutes. Peel off the skin, remove seeds, and chop.
In a large pot, heat olive oil over medium heat. Sauté diced onion for 5 minutes until translucent, then add minced garlic and cook for 1-2 minutes until fragrant.
Add chopped roasted poblano peppers and ground cumin to the pot. Stir and cook for 2 minutes.
Pour in vegetable broth and bring to a boil. Reduce heat and simmer for 15 minutes.
Blend the soup until smooth using an immersion blender or countertop blender.
Stir in heavy cream and lime juice. Season with salt and pepper to taste. Heat through for 5 minutes.
Serve the soup in bowls, garnished with fresh cilantro.