1 tablespoon vegetable oil
2 green bell peppers, stems and seeds discarded, finely diced
1 large onion, finely diced
2 cloves garlic, minced on a microplane grater
1 jalapeño or serrano pepper, stems and seeds discarded, finely chopped
1 teaspoon ground cumin
1/2 teaspoon dried chili flakes
1 chipotle chili packed in adobo, finely chopped, plus 1 tablespoon adobo sauce from can (optional)
1 quart homemade or low-sodium canned chicken broth
2 (15-ounce) cans black beans, with liquid
2 bay leaves
Kosher salt

To serve (all optional):
Roughly chopped cilantro leaves
Mexican-style sour cream
Diced avocado
Diced red onion