I cooked a ham over Christmas so I had ham stock in the freezer; which means pea soup. But I didn’t have many peas in the freezer so I added some Puy lentils (those little tiny green French ones). And it was very nice. The earthiness of the lentils and the freshness of the peas worked well together.
I chopped up a potato and an onion and sweated them down for a bit, then added the ham stock, brought it up to the boil, added the lentils and simmered them for about 40 minutes. Then I added some frozen peas, simmered it for another 5 or 10 minutes, and blitzed it with a blender. It will probably be improved with a little seasoning, but bear in mind if you’re using home-made ham stock it may be a bit salty already.
I would have added some chunks of ham if I’d had any left, but it didn’t need them. And if you were being really perfectionist for some reason—like the Queen coming to dinner—you could pass the soup through a sieve before serving; but again, it was fine as it was.