Senate Bean Soup

2 lbs navy beans
4 quarts water
1 onion, chopped
1/4 cup butter
2-3 pork hocks or leftover ham bone
leftover ham if using leftover ham bone
2 carrots, diced (optional)
Rinse beans in hot water until white.  Put in large pot with pork hocks or ham bone with 4 quarts of water.   Bring to boil, reduce and simmer covered for 3 hours. Saute onions and carrots in butter.  Remove pork hocks or ham bone and let cool.  Take 2 cups of the simmered beans, puree and add back to pot with sauted onions and carrots (if using).  Remove any meat from bones and add to pot with any leftover ham thats been cut to bite size pieces.  Season to taste with salt and pepper. 
Note: Can add optional 2 boulion cubes for added flavour.