01 -
Heat oven to 190°C / 375°F. Simmer 1 cm potato cubes in water for 7–9 minutes until just tender, then drain.
02 -
Heat oil in a 23 cm ovenproof nonstick skillet over medium heat. Cook onion 5 minutes until soft, then add drained potatoes and cook 3 minutes.
03 -
Add spinach and stir until wilted and excess moisture has evaporated. Spread the vegetables evenly across the skillet.
04 -
Whisk eggs, milk, salt and pepper just until combined. Pour over the vegetables and scatter feta evenly on top.
05 -
Cook over medium-low heat for 2 minutes, then transfer to the oven for 12–16 minutes until the center is set and reaches 71°C / 160°F.
06 -
Rest 5 minutes before cutting into four wedges. The center should be tender, with no liquid egg; protect the hot skillet handle.
07 -
Refrigerate cooled leftovers within two hours for up to three days. Reheat until hot throughout.