In a slow cooker combine split peas, onion, carrots, celery, garlic, thyme, ginger, and red pepper flakes. Pour broth over and add ham bone, if using. Season with salt and pepper.
Cook on high for 4 to 5 hours or low for 6 to 8, until peas are completely soft.
Remove ham bone from slow cooker and shred any remaining meat. Add meat back to slow cooker.
Top with Parmesan before serving.
