How to Make It
Heat 2 tablespoons of the oil in a large pot over medium heat. Add the poblano, garlic, all but ⅓ cup of the onion, ¾ teaspoon salt, and ½ teaspoon pepper.
Cook, stirring occasionally, until the vegetables are tender, 8 to 10 minutes. Stir in the cumin.
Add the beans, lager, and ½ cup water. Mash some of the beans with a fork or potato masher. Bring to a boil.
Reduce heat and simmer, stirring occasionally, until the soup is slightly thickened, 6 to 8 minutes.
Meanwhile, heat broiler. Place the jalapeños on a broilerproof baking sheet and broil until charred, 2 to 3 minutes. Slice crosswise.
In a small bowl, toss the jalapeños with the cilantro, lime juice, remaining ⅓ cup onion and 2 teaspoons oil, and ¼ teaspoon each salt and pepper. Serve with the soup.