Courgette and Smoked Cheese Frittata (4-6)

I already have a few recipes for courgette frittata on my site but could not resist trying this one from Thomasina Miers. The courgettes are roasted in the oven first, and the smoked cheese works really well, giving an almost meaty flavour. You can buy Scamorza ( smoked Mozzarella) in most Italian delicatessens and some larger supermarkets, but if you cant find this then use ordinary mozzarella.