Baking, instead of boiling, makes this version of mashed potatoes more flavorful.
Preheat your oven to 350°F. Line a sheet pan with aluminum foil, and separate a smaller square of foil for wrapping your head of garlic in. Use the butter wrappers to grease a 9"x13" casserole dish.
Drizzle 1 1/2 tablespoons of the vegetable oil over the potatoes' skins. Massage the oil into the skins. Pierce the surface of the potatoes with a fork to allow steam to escape while they bake.
Slice off the tip of the garlic (the end without the hairy root), then nestle it into the smaller piece of foil. Pour the remaining vegetable oil over the garlic and close the pouch of foil.
Bake the potatoes for 45 minutes-1 hour, or until a knife inserted into the largest potato meets little, to no, resistance.
Once the potatoes have finished baking, cover the sheet pan with a kitchen towel and allow the trapped moisture to steam the skins of the potatoes for 10 minutes. Carefully peel the skins from the potatoes. Discard the skins.
Reduce the oven's temperature to 170°F (or set to "Warm").
Place the peeled potatoes into a large mixing bowl. Unwrap the head of garlic, and squeeze the soft pulp into the bowl with the potatoes by pressing on the stem end.
Using a potato masher, smash the potatoes and garlic together until no large chunks remain.
Cut 1 stick of butter into 1/2" cubes, then add it, and the cubed cream cheese, to the potatoes.
Season the potatoes with the salt, pepper, nutmeg, and chopped parsley. Stir to combine the mixture.
Add the half-and-half and the sour cream. Stir the mixture until everything is completely blended.
Transfer the potatoes to the casserole dish and smooth it into an even layer.
Slice the remaining stick of butter into pats a 1/2" thick. Dot the top of your mashed potatoes with the butter and cover the pan with foil.
Place the dish in the warm oven and allow the potatoes to warm through, about 20 minutes.
After the potatoes have been warmed, remove the dish from the oven and uncover. Stir the melted butter into the potatoes and garnish with more chopped flat leaf parsley.
Serve while piping hot.
The mashed potatoes may be kept in an oven, set on warm, for up to 2 hours.
If you're preparing this in advance, skip the final warming step and place the foil-covered dish into the fridge. When you're ready to warm it, allow the dish to sit at room temperature to take the chill off. Heat the potatoes in a 350°F oven for a 1/2 hour, or until warmed through.
Leftovers are good for 3 days.
This recipe freezes exceptionally well: wrap the baking dish in plastic wrap followed by a layer of heavy duty foil, then freeze up to 2 months. Allow it to thaw for 24 hours in the refrigerator before heating as instructed.