Prepare the poblano pepper by preheating the oven to broil and setting the oven rack directly under the broiler.
Line a baking sheet with foil and place the small poblano pepper on top.
Broil the pepper for 3-4 minutes or until the skin is blackened and blistered.
Carefully flip it over and broil for 3-4 minutes or until the skin is blackened and blistered. Remove from the oven, place the charred chile in a large zip-lock bag, and seal it.
Allow it to steam for 5-7 minutes. Peel off the charred skin and discard the stem and seeds. Chop the poblano and set it aside.
Cook the onion & serrano by heating the oil in a large saucepan over medium heat. Add the onion and cook, stirring often, for 2 minutes.
Add the garlic, cumin, coriander, chili powder, paprkia, oregano, sea salt, and freshly cracked black pepper, and cook, stirring constantly, for 1 minute.
Add drained black beans, chicken broth, and 2 tablespoons of chopped roasted poblano (saving any remaining for another recipe), and bring to a boil.
Reduce to low and cook for 10 minutes, stirring occasionally. Taste and re-season if needed.
Serve the beans with a sprinkling of chopped cilantro and cotija cheese, if desired. Enjoy.