Can You Make Good Bean Soup without a Ham Bone?

Last week, my DH and I made a pot of some of the best navy bean soup we've ever had. We used the ham bone from our DD's Christmas Ham which had been frozen since the holidays. I'd love to make it more often than the once a year when we have a ham bone available.

What could you use in place of the ham bone to flavor the soup? I'd appreciate any ideas you can share. Nothing like a bowl of hearty bean soup in the cold winter months to warm you up!

Linda