Brown the beef short ribs with salt and black pepper in a skillet with olive oil, then transfer to the slow cooker.

Sauté chopped onion in the same skillet until softened, then add minced garlic. Transfer to the slow cooker.

Combine beef broth, red wine, crushed tomatoes, tomato paste, thyme, and rosemary in the slow cooker. Set on low for 8 hours.

Prepare polenta by boiling water, whisking in polenta, and cooking until thickened. Stir in butter and Parmesan cheese.

Serve beef short ribs over creamy polenta, garnishing with fresh herbs or additional Parmesan if desired.