Preheat oven to 400°F (200°C). Line a baking sheet with aluminum foil, leaving enough on the ends to create a packet.
Peel and discard the papery outer layer of the garlic bulbs, keeping the bulbs intact.
Cut off the top ½ inch of each garlic bulb to expose the cloves.
Place the garlic heads, cut side up, on the lined baking sheet. Drizzle with oil.
Fold the aluminum foil over the garlic, creating a large packet.
Bake the garlic for 60-70 minutes, or until the cloves are soft and deep golden brown.
Set the roasted garlic aside to cool.
Place the potatoes into a large pot. Cover with water.
Bring to a boil over medium-high heat. Cook for about 25 minutes, or until fork-tender.
Drain the potatoes and return them to the pot, off the heat.
Lightly mash the potatoes in the pot.
Add the butter and heavy cream to the potatoes. Mash the mixture to your desired consistency.
Squeeze all of the roasted garlic cloves into a medium bowl, discarding the remaining skin.
Mash the garlic until smooth. (This makes about 1 cup.)
Add the mashed garlic, salt, and pepper to the potatoes. Mix well.
Serve the mashed potatoes warm, topped with more melted butter and fresh parsley.