Winner for me is to roast carrot, onion and parsnip in the oven with a bit of curry powder sprinkled on top, when slightly brown transfer into the slow cooker with green lentils and vegetable stock and leave for a couple of hours. You can add as much or as little stock as you want depending on the consistency you’re after. Sometimes I leave everything chunky and make it more if a casserole other times I chop the veg quite small and add plenty of stock ti make it more of a soup.