Add the broccoli to a saucepan of boiling water and cook for 3 minutes, then drain into a colander. Brush the insides of a 12-section nonstick muffin tin with a little oil, then divide both the broccoli and the chicken between the sections.
Beat the eggs, milk and Parmesan together in a jug, season generously, then pour the mixture over the broccoli and chicken.
Bake in a preheated oven, 190°C (375°F), Gas Mark 5, for 15 minutes until well risen and golden. Loosen the edges of the frittatas, then turn out and serve with a tomato salad or baked beans.