1

Cook potatoes in large pot of boiling salted water until tender, about 25 minutes. Drain potatoes. Return to same pot. Stir over medium heat until excess moisture evaporates, about 1 minute; remove from heat. Add 5 Tablespoons butter to potatoes; mash well. Add 2/3 cup milk and mix, adding more milk by Tablespoonfuls to reach desired consistency. Season potatoes to taste with salt and pepper.

2

Melt 3 Tablespoons butter in large skillet over medium-high heat. Add half of mushrooms; sauté until beginning to soften, about 3 minutes. Add remaining mushrooms and shallots. Sauté until juices evaporate and mushrooms brown, about 12 minutes; season with salt and pepper. (Potatoes and mushrooms can be prepared 2 hours ahead. Let stand separately at room temperature. Rewarm separately over medium heat before continuing.)

3

Mix 2/3 of mushrooms into potatoes. Mound in bowl. Top with remaining mushrooms; sprinkle with chives.