2 large russet potato, peeled and cut as for mashed potatoes
½ cup coarsely chopped onion
½ cup fresh or frozen peas (optional)
2 cups milk
2 tsp. butter
salt and pepper to taste
Cover potato and onion with water and cook until potatoes are tender, about 20 minutes. (If using peas, add to the pot for the last 5 minutes of cooking time.) Drain carefully, so the onions don't go down the drain. Add milk and butter and heat gently until milk is warm. Add salt to taste and a good grinding of fresh black pepper.