Heat a large nonstick skillet over medium-high heat. Add beef; cook 5 minutes or until browned, stirring occasionally. Drain. Place beef in a 4-quart electric slow cooker; sprinkle with salt.
Return pan to medium-high heat. Add onion and garlic; saute 5 minutes or until tender. Spoon onion mixture over beef. Combine beef broth and next 6 ingredients (through jalapeño); pour over beef. Cover and cook on LOW for 6 hours.
Stir in spinach. Cover and cook on LOW for 15 minutes or just until spinach wilts. Serve beef mixture over rice; sprinkle with basil leaves.