1. Preheat oven to 375 degrees. Chop ¿ inch off the tops of the garlic heads so that the cloves are exposed. Place on aluminum foil and drizzle with olive oil, then wrap and seal the foil. Bake until the garlic heads are soft and golden brown - it should take about one hour. Set aside and let cool.
2. Peel and chop potatoes into three-inch pieces, place in a large pot and cover with cold water. Bring to a boil, then reduce heat and simmer until tender (about 30 minutes). Meanwhile, push garlic cloves out of skin and mash with a fork. Drain potatoes in a colander and return to the pot at low heat. Add butter in ff-inch slices and the mashed garlic. Heat heavy cream to lukewarm (in a saucepan or microwave) then gradually add to potatoes while mashing to desired consistency. Add salt and pepper to taste.