One of my favorite things mom would make when I was a kid was potato soup. We'd eat it with buttered crackers and it always hit the spot on the cool day.
About 6 - 8 potatoes, peeled and diced small
half of an onion, diced
water, enough to completely cover your potatoes
About a cup of milk
A stick of butter
Put potatoes and onion in a pot and cover just above top with water. Add a 1/2 teaspoon or so of salt. Bring to a boil. Reduce to a simmer for about 15 minutes. Add milk and butter, continue boiling about 2 two more minutes. Turn off heat, scoop into bowl and season with salt and pepper. Parsley is also a nice garnish.