Brown the ground beef in a skillet over medium heat.
Add chopped onions and minced garlic, cooking until softened.
Transfer the meat mixture to the slow cooker.
Stir in black beans, corn, diced tomatoes, chicken broth, chili powder, and cumin.
Season with salt and pepper to taste.
Cover and cook on low for 6-8 hours or high for 3-4 hours.
Before serving, stir in the shredded cheese until melted.
Serve hot, garnished with sour cream and cilantro if desired.