BRING a pot of lightly salted water to a boil.
ADD the potatoes and garlic and cook until tender, 20 to 25 minutes.
DRAIN.
MASH with a potato masher or hand mixer.
STIR in the butter and salt.
With a wooden spoon or hand mixer, BEAT in the coconut milk
COVER and keep warm.
Meanwhile, in a large skillet, COOK the prosciutto over medium heat, stirring occasionally, for about 3 minutes.
ADD the onion and cook, stirring frequently, until the prosciutto is crispy and the onion is tender and brown on some of the edges, about 8 minutes more.
ADD the vinegar to the pan and stir to scrape up the browned bits on the bottom.
SPOON the onion mixture over the mashed potatoes and sprinkle with the pine nuts.