1Heat 1 1/2 teaspoons of the oil in 12-inch nonstick skillet on medium-high heat; season beef with salt and pepper. Add half the beef to heated skillet and brown on at least two sides, about 4 to 6 minutes. Transfer beef to 3 1/2 to 4 1/2 -quart slow cooker. Add 1 1/2 teaspoons oil to skillet and repeat for remaining beef.
2Add remaining 1 tablespoon oil to skillet and cook onion for 2 to 3 minutes, until starting to brown and softened. Stir in garlic and cook until fragrant, about 20 to 30 seconds. Transfer mixture to slow cooker.
3Add diced tomatoes, green chiles, chipotle, water, cornmeal and cumin to slow cooker and stir to combine. Cover and cook on Low heat setting for 8 to 9 hours, until beef is tender. Serve with toppings, if desired.