Slow Cooker Black Bean Chili

Name: Slow Cooker Black Bean Chili
Ingredients: 2 tablespoons olive oil; 1 large onion, diced; 1 medium red bell pepper, cored, seeded, and diced; 3 cloves garlic, minced; 2 tablespoons unsweetened natural cocoa powder; 2 tablespoons chili powder; 2 teaspoons ground cumin; 1 teaspoon kosher salt; 1/4 teaspoon freshly ground black pepper; 1/4 teaspoon cayenne pepper; 1 pound dried black beans; 1 (28-ounce) can diced fire-roasted tomatoes; 5 cups (40 ounces) low-sodium vegetable broth; Green onions, green parts only, thinly sliced; Chopped fresh cilantro