You and your guests will be utterly charmed when you see how easily mashed potatoes can be transformed into a gaggle of ghosts. Simply form them into pointy mounds and then personify—no, make that "ghostify"—them with seed "eyes." Don't be surprised if these become a new family must-have for Halloweens to come.

4 pounds large boiling potatoes (preferably white-fleshed)

3/4 stick unsalted butter, cut into pieces

1 1/4 cups whole milk

3 large egg yolks

Nigella seeds (sometimes mislabeled "black onion seeds") or caraway seeds for garnish

Equipment: a potato ricer or a food mill fitted with medium disk; a pastry bag with 3/4-inch plain tip

Preparation Peel and quarter potatoes, then cover with water in a 4-quart pot and season well with salt. Simmer, partially covered, until tender, 15 to 20 minutes. While potatoes are simmering, heat butter and milk in a small saucepan until butter is melted. Remove from heat and cover to keep warm. Preheat oven to 400°F with rack in middle. Drain potatoes and force through ricer into a large bowl (or mixer bowl if using stand mixer). Beat in milk mixture, yolks, and 1/2 teaspoon each of salt and pepper with an electric mixer at low speed until combined. Spread about one-third of potatoes in a buttered 1 1/2-quart shallow ovenproof dish. Transfer remaining potatoes to pastry bag. Pipe potatoes close together into 2 1/2- to 3-inch-high pointed mounds to form "'ghosts" and garnish each mound with 2 seeds for "eyes." Bake until tips of ghosts are golden and potatoes are firm, 20 to 25 minutes. Cooks' Note:Potatoes can be piped into dish 1 day ahead and chilled, loosely covered with plastic wrap.