First, chop the potatoes into one-inch chunks and leave the peels on if desired. (If not organic, I suggest removing the peels first.) Set aside.Dice the celery into small pieces or process in the food processor. Set aside.Add potatoes, celery, dry lentils and mushrooms into the slow cooker.Cover with the water and broth, then stir in the herbs and spices.Lastly, add in the ¼ of an onion and clove of garlic and leave them whole. I actually remove them after cooking with the bay leaf for digestion reasons, but you can also chop and dice them into small pieces before adding them if you want to leave them in.Cook on high for 4 hours or until the potatoes and lentils are tender.Remove the bay leaf, onion, and garlic clove; discard.Stir everything together, then purée the soup while still in the slow cooker with an immersion blender or handheld mixer. Alternatively, you can let it cool for 5-10 minutes, then add it to your blender and purée it there instead.Serve the soup, sprinkle with additional salt and/or pepper if desired, and enjoy!