Place ham hock in a 5 quart slow cooker. Combine the split peas, chicken stock, bouillon, carrot, celery, potatoes, garlic powder, oregano, bay leaves, and onion to the slow cooker.
Cover, and cook on High for 4 to 5 hours or on Low for 8-9 hours.
Remove bay leaves and ham hock. Remove any large pieces of ham and set aside.
Using an immersion blender, purée soup in the slow cooker to thicken it. You can leave some chunks to give the soup some texture or blend it until it's smooth.
Taste soup and season with salt and additional pepper if needed. Add pepper.
Remove any pieces of ham from the bone and return it to the slow cooker. Stir to combine with soup.
To serve, top each bowl with grated Parmesan cheese.