Whisk the eggs, cream and parsley in a mixing bowl. Season well with salt and pepper to taste.
Melt the butter in a large, non-stick frying pan over high heat. Reduce the heat to low-medium. Pour in half of the egg mixture. Use a slotted turner to spread out the egg mixture to create a thin, even layer. Cook for 1 minute or until the egg mixture is set, then arrange half of the ham and mozzarella over the thin egg mixture, leaving 2cm clearance around the edges. Fold and roll the frittata over to enclose the ham and mozzarella, leaving 2cm unrolled. Move the frittata over to one side. Pour in the remaining egg mixture directly beside the unrolled frittata so that the newly added egg mixture will stick to it. Once again, use the slotted turner to spread the egg mixture away from the ham and cheese rolled frittata to create a thin layer. Arrange the remaining ham and mozzarella over the egg mixture, once again leaving a 2cm clearance around the edges. Roll the frittata so that you end up with a long rectangular frittata in the pan.
Once completely rolled, cook for a further 2-3 minutes or until the frittata is golden and cooked through. Transfer the Frittata (rolled omelette) of ham and mozzarella to a serving plate and allow to cool for a few minutes before slicing.
Serve immediately or at room temperature – buon appetito.