In a medium or large slow cooker, combine onion, garlic, chopped jalapeño, chicken, oregano, cumin, salt, black pepper, and cayenne (if using). Cover with beans, including liquid from one can, broth, and chiles and stir to combine.

Cover and cook on High for 3 to 4 hours, or Low for 8 hours, until an instant-read thermometer inserted into thickest part of chicken registers 165°.

Transfer chicken to a cutting board. Let cool slightly, then shred.

Transfer 3/4 cup beans (it’s okay if some veggies come along) and liquid to a large bowl or measuring cup. Using a fork or immersion blender, puree beans. Return shredded chicken and pureed beans to slow cooker. Add corn and sour cream and cook on High until corn is cooked through, about 30 minutes more.

Season with more salt and black pepper, if needed. Top with sour cream, sliced jalapeño, avocado, cilantro, and a squeeze of lime juice.