Photograph: Jonathan Gregson
Soak the dried porcini in plenty of hot water until soft. Drain, rinse well and check for any grit, then roughly chop.
Heat a large nonstick frying pan and melt half the butter. Once it's stopped sizzling, add the beaten eggs and lower the heat. Cook the mixture slowly, stirring occasionally, for 8-10 minutes. When it's almost cooked, but still creamy, remove from the heat and mix in the chopped porcini, the rest of the butter and the handful of cheese. Mix lightly and check the seasoning.
Griddle or toast the slices of sourdough, then rub with rosemary sprigs to flavour the bread. Tip the scrambled eggs on to the plates and add the prosciutto. Scatter with the extra parmesan and serve with the rosemary bruschetta and the extra rosemary to garnish.