This creamy soup actually has no cream! The long slow cooking of the vegetables creates a wonderfully smooth texture and rich flavor (helped out with a flavor boost from the bacon.)
When peeling the rutabaga, take a thick layer from the vegetable. You can double peel it, first removing the outer layer and then peeling again to reach the creamy yellow interior.
In a large, heavy-bottomed pot, cook the bacon over low heat to render the fat. Watch the bacon to make sure it doesn't become too crisp. This will take 15 to 20 minutes, but check often and lower the heat if the edges of the bacon begin to burn. While the bacon fat is coming off of the meat, prep the rest of your vegetables (chop the potato into larger pieces than the rutabaga; they cook a lot faster.)
Add the onion, carrot, celery, bay leaf and thyme to the bacon meat and bacon fat. Cover and sweat these vegetables about half hour. Stir often, and keep the heat low.
Add the potatoes, the rutabaga, and enough water or stock to cover all the vegetables. Raise the heat to medium. Cook the soup for about 1 hour 15 minutes to 1 hour 30 minutes. The rutabaga pieces must be very soft when done: you should be able to smash them between your fingers.
Let the soup cool to just warm, and purée using an immersion blender, Vitamix (don't froth too much air into it), or food mill.
Pass the puréed soup through a mesh screen or fine strainer and press using a ladle or large spoon. Discard the gummy starches and proteins that collect. Return the soup to the pan and reheat it, seasoning well with salt and pepper.