Begin by peeling and thinly slicing your Yukon Gold potatoes. A mandoline slicer can be handy for achieving uniform thickness. Slice the onion into thin rings. Set aside.
In a large skillet, pour in the olive oil and heat it over medium heat. You want enough oil to cover the bottom of the pan, which will help cook the potatoes evenly.
Once the oil is hot, add the sliced potatoes and onions to the skillet. Sprinkle with salt and pepper. Cook for about 15-20 minutes, stirring occasionally, until the potatoes are tender but not browned. They should be soft and slightly translucent.
Once cooked, use a slotted spoon to transfer the potatoes and onions to a bowl. Let them cool slightly, then drain the excess oil from the skillet, leaving just a tablespoon or so for cooking the omelette.
In a mixing bowl, crack the six eggs and whisk them until fully combined. Season with a pinch of salt and pepper.
Gently fold the cooked potatoes and onions into the eggs, ensuring they are evenly distributed.
Return the skillet to the stove over medium heat. Pour the egg mixture into the skillet and cook for about 5-7 minutes, or until the edges begin to set but the center is still slightly runny.
Using a large plate, carefully flip the tortilla. Slide it back into the skillet, uncooked side down, and cook for an additional 5-7 minutes until fully set.
Once the tortilla is cooked through, slide it onto a serving plate. Let it cool slightly before garnishing with chopped chives. Slice into wedges and serve warm or at room temperature.
