Has to be spuds with the skin still on (vitamin C lives just under the skin and usually gets peeled off), whole raw milk (vitamins A & some Bs and some protein and a lot of fat) OR butter, and a supplemental protein source - such as oily fish (vitamin D) or meat or cheese. If you peel the spuds, you’ll need a supplement such as fruit. The classic Irish diet that the potato famine of 1840s pretty much wiped out and triggered mass migration to USA and here.