Heat 1 tbsp oil in a medium non-stick frying pan. Add the onion and cook for 5 minutes until softened. Add the garlic, a few gratings of fresh nutmeg, the chilli and lamb, and cook for 1-2 minutes. Stir in the spinach and cook until wilted, then tip the contents of the pan into a bowl.
In a separate bowl, beat together the eggs and milk and season well. Preheat the grill to medium.
Wipe the pan clean with kitchen paper. Add the remaining oil and heat over a medium heat for a few seconds. Pour in the eggs and cook for 1-2 minutes, stirring occasionally, until it looks very lightly scrambled, but is still mainly liquid. Add the lamb mixture, stir, then cook for 4-5 minutes until the base of the frittata is set.
Transfer the pan to a preheated grill and cook for 3-4 minutes until set. Leave to stand for a few minutes before turning out and slicing. Serve with the salad.