Here's the Cream of Lentil Soup recipe. I'll type what the actual recipe says, then describe what I actually do.
16 oz dried lentils
1 onion, chopped
1 clove garlic, minced I use about six times as much
1-3 carrots, chopped
1 bunch celery, chopped I usually use one third or half of a bunch
3 cups water you will really need more than this
1 cup heavy cream
salt and pepper, to taste
Soak the lentils overnight in six cups of water. In the morning, drain the lentils and put them in the crockpot with the onion, garlic and celery. Add the 3 cups of water to the crockpot. Cook on low for 8-10 hours; the lentils will be soft and mushy. Turn off the crockpot and stir in the cream. Stir in salt and pepper.
I don't think you really have to soak the lentils, and I'm not sure why it calls to. I've done it both ways (soaked and unsoaked) and it turns out fine. Regardless of whether you soak or not three cups of water is not enough. I think this has to be a misprint in the cookbook, you really need closer to five cups of water. Six is a bit too much, IMO. If I don't have eight hours, I usually cook it on high in the crockpot until it is done then turn it down to low. If you cook it on the stovetop, it should take about an hour or so. You can leave out the cream, and it is still good (but not as good). I always add the salt and pepper before the end of cooking.