Well the ham stock was ideal for making soup, not too salty, so all that soaking I did paid off. The ham is delicious too, so that's a double win. Before Christmas I bought a pack of big flat mushrooms, going cheap for 50p. I didn't want to waste them so about an hour ago I made them into soup, as follows:

In my cast iron casserole I fried some shallots and some chopped celery in olive oil. After about 15 minutes I crumbled up those mushrooms and threw them in. Once they'd reduced down a bit, I added about two pints of the ham stock and let it all simmer for five minutes. I carried the pot to the sink and whizzed it all to a rubbly broth with my stick blender. I put it back on the heat and added a pack of Merchant Gourmet pre-cooked Puy lentils (which are an excellent ingredient). After a few more minutes I decided to whizz the soup again. The texture was great for drinking out of a mug, thick and hearty but not too thick, and the seasoning just needed a quick tweak. It's delicious, and a big mug of that was all I needed for my lunch. There plenty for both of us tomorrow too. I've seen other mushroomy soup recipes that call for Worcestershire sauce (weird...) or cream, but I honestly thought that further embellishments were unnecessary. During the season of eating tons of rich stuff, something low-fat and nutritious like this is just what's called for, I reckon.