Preheat the oven to 425 F.

Scrub potatoes and prick them with a fork in several places. Place the potatoes on a rack and bake for 45 to 55 minutes or until very tender.

Meanwhile (about 10 minutes before the potatoes are done), in a skillet over medium heat, melt the butter. Sauté the mushrooms until they are tender and the liquid has evaporated; set aside.

Just before the potatoes are done, heat the milk in a saucepan or microwave just until hot.

Slice a thin slice from the top of each potato. Scoop the potato out into a bowl leaving shell intact.

Add the heated milk to the potatoes in the bowl and beat until fluffy. Season with salt and pepper, to taste.

Stir the hot mushrooms and butter into the potatoes.

Pile the potato mixture into the shells.

Sprinkle with the shredded cheese.

Place the potatoes back in the oven and bake until browned.

Garnish with chives or parsley.