One large russet potato, peeled and cut as for mashed potatoes
4 Tbsp. coarsely chopped onion
1/2 tsp. salt
1 cup milk, or non-dairy milk
pepper to taste
Cover potato and onion with water, add salt, and cook until potatoes are tender, about 20 minutes. Drain carefully, so the onions don't go down the drain. Heat milk until just warm. Mash potatoes and onions with a fork, leaving some small lumps. (For elegant creamy soup, you can run this through a blender, but I like the lumps.) Stir in the milk; you may need to use more, depending on the size of the potato and how thick you like your soup. Add a good grinding of fresh black pepper and serve immediately.