Mashed Potatoes with Mushrooms

Bahan-bahan (8 porsi)

• 5 pounds Russet potatoes, (peeled and cut into 1½-inch cubes)
• 8 tablespoons (1 stick) butter, (divided)
• 2/3 cup (or more) whole milk
• salt and pepper, (to taste)
• 1½ pounds sliced mushrooms ((crimini, baby bella or white))
• 1/2 cup chopped shallots
• 2 tablespoons chopped fresh chives