These make a great accompaniment for eggs.
Use yellow or red potatoes, like Yukon Gold, not the brown russet potatoes.
Cut them into uniform-sized chunks, like 1/2″ x 1/2″ x 1″ or thereabouts. (The exact size isn’t critical, but avoid having a mix of big chunks and little bits, because you want them all to cook evenly.)
Add the potatoes to a pot of water, put it on high heat, and bring to a boil for five minutes, then drain.
Heat a large skillet on medium heat and add a generous dash of oil.
Arrange the potatoes in an even layer so they all have a flat side touching the pan and allow to cook until that side is lightly browned, about five minutes.
While the potatoes are browning, dice an onion. (Optionally include other vegetables, like a bell pepper, a very-finely-diced carrot, some scallions, a small tomato, etc.)
When the potatoes are lightly browned on one side, toss in the vegetables and use a spatula to turn everything over.
Continue to cook for about ten minutes, stirring occasionally, while you add salt and black pepper. Optionally include some paprika, dried basil, crushed garlic, or other seasonings.
Periodically check for doneness and remove when the onions are well cooked and the potatoes are done all the way through.