01 - Preheat oven to 400°F. Slice the top off the garlic head to expose the cloves. Drizzle with olive oil, wrap in aluminum foil, and roast for 35 to 40 minutes until soft and golden. Remove from oven and let cool.
02 - While garlic roasts, place potatoes in a large pot and cover with cold water. Add a generous pinch of salt. Bring to a boil, reduce to a simmer, and cook until fork-tender, approximately 15 to 20 minutes.
03 - Drain potatoes thoroughly and return them to the hot pot. Allow to steam off excess moisture for 2 minutes.
04 - Squeeze the roasted garlic cloves from their skins into the potatoes. Add butter, warm milk, and cream.
05 - Mash until smooth and creamy. Season generously with salt and pepper. Taste and adjust seasoning as needed.
06 - Transfer to a serving bowl and garnish with chopped chives or parsley if desired. Serve immediately while hot.