2) In a medium ovenproof nonstick pan heat the oil over a medium flame. Add the onion and cook until it begins to soften, about five minutes. Add the broccoli and cook for another two minutes. Season with salt and a few turns of pepper.
3) Pour the egg mixture over the vegetables in the pan covering them evenly. Reduce the heat to medium-low, cover, and let cook until the egg mixture has set around the edges but is somewhat liquid in the middle, about eight minutes. Sprinkle with the cheese.
4) Meanwhile, preheat the grill. Place the pan under the grill about five centimetres from the heat until the surface is set and golden brown, one to two minutes. Be careful not to overcook or the egg mixture will become tough. Cut the frittata into eight wedges and serve.