Preheat the oven to 160 degrees Celsius/ 320 degrees Fahrenheit.
Prepare garlic: Remove the tiny garlic cloves (those that are much smaller compared to the rest of the garlic cloves from the bulbs) and use them for something else. Peel the other garlic cloves and place them in a small ovenproof dish. Add the olive oil, rub the cloves with the oil
Bake for about 20 minutes, mixing half time again, or until lightly golden and very tender.
Puree garlic in a small food processor or with a handheld blender, together with their olive oil.
Prepare potatoes: In the meantime peel and cube the potatoes. Cook them in salted water for about 15 – 20 minutes or until fork-tender. Drain very well. Mash them with the potato ricer or a regular potato masher.
Combine: Heat the milk in a small pot. Add it to the mashed potatoes with the pureed roasted garlic and their oil, butter, and grated Parmesan.
Adjust: Add salt and freshly ground black pepper to taste. Be generous with the salt but adjust the quantity as required; you will need less salt if using salted butter for the mashed potatoes. Mix well with a wooden spoon. Stir in the chopped parsley and serve immediately.
I always recommend using freshly grated Parmesan; there is no comparison between that and the already grated one you can find in the supermarket.