Joel Robuchon, the maker of the most celebrated mashed potato in the world, uses a waxy variety of potato. I am no Joel Robuchon; and I am not as lavish with the butter and cream as he is. The effort of breaking down the firm textures, I find, causes the potatoes to become glutinous.
(A reader has pointed out to me a mistake in my book. Sticky rice, I wrote, was sometimes known as "glutenous", although it contained no gluten. I was borrowing from Sri Owen, but adjusting her spelling: in The Rice Book, she assumed that the term "glutinous rice" derived from the protein -- it was "either bad English or bad science", she complained. She and I should have checked our dictionaries, where we would have discovered that "glutinous" was an unrelated word, derived from the Latin word for glue.)
Crushed new potatoes, though, are lovely: they preserve the distinctive qualities of the potato, but have the richness of mash. Drain them, and crush them with a fork, preserving a few lumps; stir in a generous portion of butter with some salt, and with pepper if you like. It is a fine way to enjoy the Jerseys that are starting to come on to the market.