Put the potatoes in a 4-quart saucepan with enough cool water to cover by at least 1 inch. Add 1 tsp. salt and bring to a boil. Turn the heat down and cook at a gentle boil, skimming off any foam, until the potatoes can be easily pierced with a fork, about 15 minutes.
Drain well in a colander, letting the steam rise off the potatoes for a few minutes.
Meanwhile, heat the milk and butter in the saucepan until the butter is melted. Season with 1 tsp. salt, 1/2 tsp. pepper, and a pinch of nutmeg.
For a rustic texture, return the potatoes to the pan and mash with a potato masher to the consistency you like.
For a smooth texture, pass the potatoes through a ricer or food mill into the saucepan and stir to combine. (For really smooth potatoes, whisk the potatoes briefly.)
Season to taste with more salt and pepper and thin with additional milk, if necessary, before serving.
ROSEMARY AND GARLIC
Follow the recipe but add 2 large peeled cloves of garlic to the potatoes at the start of cooking. Then add 2 tsp. finely chopped fresh rosemary along with the milk and butter. This is spectacular with roast lamb.
SAFFRON AND SHALLOT
Follow the recipe but heat only the butter. Add 1 small finely chopped shallot and cook, stirring occasionally, until soft, about 3 minutes. Add the milk and 2 pinches of saffron threads and bring to a simmer before adding the potatoes. Serve with scallops or shrimp or some poached smoked haddock.
Follow the recipe and stir in 1 Tbs. each of finely chopped fresh chives, parsley, and dill just before serving. This is especially good with fish.
nutrition information (per serving):
Calories (kcal): 410; Fat (g): 25; Fat Calories (kcal): 220; Saturated Fat (g): 15; Protein (g): 5; Monounsaturated Fat (g): 6; Carbohydrates (g): 45; Polyunsaturated Fat (g): 1; Sodium (mg): 340; Cholesterol (mg): 65; Fiber (g): 4.