Cook the potatoes in a saucepan of lightly salted boiling water for 2–3 minutes until just tender. Meanwhile, heat the oil in a 28 cm (11 inch) ovenproof frying pan, add the spinach and cook for 1 minute until wilted.
Beat the eggs in a small bowl with the chives and season to taste. Drain the potatoes and stir into the pan with the spinach, then add the eggs and stir briefly. Cook without stirring over a medium heat for 3–4 minutes until almost set.
Dot the ricotta over the frittata and continue to cook under a preheated hot grill for 2 minutes until golden. Cut into wedges and serve immediately.