Start with the preparation for the ‘polpettine’. Chop the bacon rashers and mix in the mince together with the egg, 100g cheese, chopped parsley and lemon zest, bread crumbs and a spoon of cream. Season the mixture, combine well and roll into a cigar shape, roll in cling film and freeze slightly. Remove from freezer and cling film, cut into mini ‘polpette’, small meat patties. Bake the patties in a moderate oven for a few minutes until sealed. To make the sauce, cook the onion until soft in the butter. Add the mushrooms, cook for 2 minutes, stir in the cream, the polpettine, parsley and cracked pepper. Next add the cooked spaghetti and mix with sauce. Remove from heat and stir in the egg yolks and the remaining cheese.