Peel the potatoes, cut them top to bottom, then in half-moon slices about as thick as three stacked quarters.
Slice the onions the same way as the potatoes, but half as thick. Combine the potatoes and onions in a 10-inch skillet. Toss them together until evenly distributed.
Pour the olive oil over the potatoes and onions, and place over medium-high heat. Stir the pan gently every minute or so, turning the contents over so they don't brown. You are not frying them. Cook until the potatoes are soft and no crunch remains in the onions.
When that point is reached, move the skillet off the burner and let it sit there for eight to ten minutes, until it's just barely warm to the touch.
With a slotted spoon, transfer the potato-onion mixture into the bowl of beaten eggs. (Save the excess olive oil.) Add the salt and pepper to the eggs, potatoes and onions, and toss lightly.
Cover the bowl and put it in the refrigerator for two hours to overnight.
When ready to serve, heat a skillet (preferably nonstick) over the lowest possible heat with the leftover olive oil. (You need about 2 Tbs. of oil; add more if necessary.) Add the egg-potato-onion concoction to the pan and cook until you see the egg component starting to congeal.
Get a plate big enough to cover the skillet completely. Place it on top of the skillet, hold it in place, and turn both the plate and the skillet over, so the mixture is now upside-down on the plate. With a jerk of the wrist, slip the pancake back into the skillet, and cook until browned--about four minutes. Let it cool, slice into pie slices, and serve..