Of course best is a matter of personal preference but here is how I make them. Wash but don't peel the potatoes. There are a lot of nutrients and flavor in the skin. Cut them up and boil them until they are completely cooked not al dente. The skin will be starting to come off. Drain them and mash them with a potato masher while they are hot. Mix in lots and lots of butter and cream. Put salt and garlic in. Thinly sliced cloves are best but garlic powder will do. I sometimes add oregano and cayenne. My mashed potatoes are always a hit once people get over the fact that I didn't peel the potatoes. You can peel them and whip them for a smoother consistency but that is whipped potatoes not mashed potatoes. Some people add sour cream. I don't.
I always use evaporated canned milk in mine. It makes them creamier. My grandmother always taught me the best mashed potatoes have plenty of salt and butter in them. And hers were to die for. My kids always love it when I put little pats of butter on top to melt and run down around the potatoes. And I always top them with fresh ground pepper.
Boil red skin potatoes with skin on. Slice them up first so they ll boil faster. Drain the water. Add a splash of milk or heavy whipping cream, butter, salt and pepper to taste. Mash with a potato masher or blind with a hand held blender.
saute' whole head of garlic, (broken up and peeled)...with whole stick butter, add chicken broth and cream,(3/4 broth to 1/4 cream) add potatoes, (I use Yukon gold...no need to Peel) cook til tender,mash,add salt and pepper to taste....delectable!!!