Indeed, the old Irish diet of milk and potatoes was pretty darn healthy. If you're trying to eat healthily, cheaply, and with a reasonable cognitive load, it's hard to go wrong with eggs, milk, and potatoes. Poor people can do this. Eggs and milk get you all the important macrominerals and fat soluble vitamins and potatoes are nature's multivitamin/multimineral. Nothing else can really touch these for depth and breadth of essential nutrients:
They scale well, so even if they're not the only things you eat, you're at least assured of not being acutely deficient of anything. Plus, it's easy to prepare lots of yummy things from them.
Now, if you're concerned with maximum longevity, you should try to add as many fruits and vegetables a day as you can to suck up phytonutrients/antioxidants.
http://nutritiondata.self.com/facts/recipe/2864450/2
They scale well, so even if they're not the only things you eat, you're at least assured of not being acutely deficient of anything. Plus, it's easy to prepare lots of yummy things from them.
Now, if you're concerned with maximum longevity, you should try to add as many fruits and vegetables a day as you can to suck up phytonutrients/antioxidants.