Start by peeling and chopping the 4 large russet potatoes into evenly sized chunks. Place the potatoes in a pot filled with salted water, ensuring they are fully submerged. Bring the water to a boil over medium-high heat, then reduce to a simmer and cook for about 15-20 minutes until the potatoes are fork-tender and easily break apart.

Once tender, drain the potatoes well and return them to the pot. Add ½ cup of heavy cream, ¼ cup of melted butter, and sprinkle in salt and pepper to taste. Use a potato masher or a hand mixer to mash the mixture until it's smooth and creamy.

Prepare a skull mold or use your hands to form the mashed potatoes into skull shapes. If using a mold, pack the potato mixture tightly to maintain the shape, then carefully invert it onto a plate. If shaping by hand, sculpt the potatoes with your fingers, ensuring they have defined features.

Slice the black olives into small circles to create eyes and cut small pieces for a mouth. Arrange the olive slices on each potato skull, pressing gently to secure them in place.

For an extra touch, finely chop fresh chives or green onions and sprinkle them atop your spooky creations. Serve your Spooky Skull Potatoes warm as a delightfully eerie side dish.