The recipe calls for 7 medium-size Russet potatoes. But if some of the potatoes are smaller than others, cut the larger ones in half. The idea is to have them all be about the same size so they cook at the same rate.
To a large pot, add cold water, salt, garlic, and the potatoes (the potatoes cook more evenly when added to cold water; if added to boiling water the outside of the potato cooks faster than the inside).
Heat the pot on medium heat and bring the water to a boil.
Cook the potatoes until a cooking fork or paring knife can easily pierce the potatoes. Be careful not to overcook the potatoes or they’ll be mushy and fall apart.
While the potatoes are cooking, in a large mixing bowl add milk, butter, salt and pepper. Set aside.
When the potatoes are done cooking strain them, being careful not to splash the very hot water. The pieces of garlic should also end up in the strainer with the potatoes.
As soon as possible while the potatoes are hot, carefully transfer them to the mixing bowl.
Using a potato masher or electric mixer, mash (or whip) the potatoes. If the mashed potatoes are too thick, stir in a bit more milk.
Stir in the cheese and give the mashed potatoes a taste test to see if more salt is needed.
The mashed potatoes should be hot enough to melt the cheese. If not, put them in a microwavable bowl and warm them at very short intervals (so not to over heat them) until the cheese is melted.
Top with butter, garnish with parsley, and serve right away while warm.