Rinse and dry the produce. Trim, deseed, and roughly chop the poblano pepper. Peel and chop the onion. Drain and rinse the cannellini beans, then set aside ½ cup for your own use in a future recipe. Peel the plantain and slice into 1-inch thick pieces on the diagonal.
Place a large pot over medium-high heat with 1 tbsp vegetable oil. Once the oil is hot, add the poblano pepper and onions and cook until softened and slightly browned, about 3 to 5 minutes. Sprinkle with salt and pepper.
To a food processor, add half of the poblano and onion mixture. Peel and add 3 cloves garlic and as much or as little of the pickled jalapeño as you’d like, and pulse until well combined and fairly smooth. Leave the remaining half of the poblano and onion mixture in the pot and off of the heat.
Return the pureed vegetables to the pot over medium heat. Add the cannellini beans, vegetable broth concentrate, Mexican oregano, cumin, coriander, and 1¼ cups water. Bring to a simmer, stirring occasionally, and cook until slightly thickened, about 5 to 7 minutes. While your soup simmers, move on to cooking the plantains.
Place a large nonstick skillet over medium-high heat and add 1 tbsp vegetable oil. Add the plantain slices and cook until golden brown, about 3 to 5 minutes per side. Sprinkle with salt.
Chop the cilantro leaves and tender stems. Chop the scallion. Squeeze the juice from the lime into the chili and season with ½ tsp of salt. Ladle white bean poblano chili into large bowls and top with the sour cream, chopped cilantro, and scallions. Serve with the crispy plantains.