Slice the top off each garlic head to expose the cloves. Drizzle with olive oil, sprinkle with salt, wrap in foil, and roast until deeply soft and golden. Let cool slightly, then squeeze cloves into a bowl and mash into a paste.

Peel and cut potatoes into evenly sized chunks. Add to a large pot of cold, well-salted water. Bring to a gentle boil and cook until fork-tender.

Drain potatoes thoroughly and return them to the hot pot for a minute to let excess moisture evaporate. This step prevents watery mashed potatoes.

Mash potatoes using a masher or ricer. Avoid blenders or food processors, which overwork starch and cause gumminess.

While potatoes are hot, add butter and roasted garlic paste. Stir gently until melted and incorporated.

Slowly add warm cream or milk, stirring until desired consistency is reached. Season with salt and pepper.

Adjust seasoning, add herbs or cheese if using, and serve immediately.