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

Drain the potatoes and return them to the pot. Add heavy cream, melted unsalted butter, along with salt and pepper to taste. Mash until smooth and creamy, ensuring no lumps.

Shape the creamy potato mixture into skull forms using a skull mold or your hands. Pack tightly to maintain shape and place on a parchment-lined baking sheet.

Preheat the oven to 375°F (190°C). Bake the skull potatoes for 15-20 minutes until the tops are golden brown and crispy.

Remove from the oven and add black olives as eyes for each skull. Garnish with fresh chives or green onions if desired and serve warm.