Peel and chop the large russet potatoes into 2-inch chunks. Place into a large pot and cover with salted cold water. Bring to a boil over medium-high heat, then reduce to a simmer and cook for 15-20 minutes until fork-tender.

Drain the potatoes and return to the pot. Mix in the heavy cream, melted butter, salt, and pepper over low heat, using a potato masher to blend until smooth.

Shape the mashed potatoes into skulls using a mold or by hand, packing tightly. Place on a parchment-lined baking sheet.

Preheat oven to 375°F (190°C). Bake shaped skulls for 15-20 minutes until slightly golden.

Use sliced black olives for the skull's eyes and garnish with fresh chives or green onions after baking.

Serve warm as a festive side dish or centerpiece, adding themed decor around the dish for ambiance.