Combine eggs and cream in a small bowl and whisk until just combined. Season to taste with salt and freshly ground black pepper.
Preheat oven to 180c. Heat a 20cm frying pan over medium heat, add butter and cook until foamy. Add beaten eggs and, using a fork, drag the set outer edge to the centre, working around the pan until the base is just set. Place pan into the oven and cook until frittata has puffed, about 5 minutes, remove and top with prosciutto slices, chèvre and parsley. Serve immediately.