Place all spud hunks in a 4-quart saucepan and add just enough cold tap water to cover. Add 1 teaspoon of the salt to the pot, cover, and bring to a boil over high heat, about 15 minutes.
Meanwhile, combine the buttermilk, cream, and garlic in a 2-quart saucepan and bring to a bare simmer over low heat, watching to make sure the mixture doesn’t boil over. Keep the mixture barely bubbling until the potatoes are done.
When the spud water boils, uncover, drop the heat to a simmer, and cook until the spuds are easily crushed with tongs, 15 to 20 minutes. Drain the potatoes, then return them to the pan and the heat. Toss and shake gently for 30 seconds or so to cook off any excess surface moisture — the drier the spuds the better.
Move the pan to a trivet, hot pad, or towel on the countertop and sprinkle with the remaining 1 teaspoon salt. Pour on about a quarter of the buttermilk mixture and start mashing. As the spuds break down, add more of the buttermilk mixture until you’re happy with the results. Remember, these are mashed potatoes, not whipped potatoes. If you over-mash in an attempt to smooth every piece, you will inevitably rupture starch granules, which can and most likely will result in gummy potatoes.
Serve straight or garnish with parsley, chopped scallions, crumbled bacon, sun dried tomatoes, grated horseradish, horseradish sauce, pesto, more bacon, sauteed mushrooms...use your imagination.