Remove the pistils from the courgette flowers and rinse them delicately. Peel the onion. Clean and rinse the parsley then chop it with the onion and the courgette flowers. Heat the oil in a pan, add the onion mix, the saffron, diluted in a glass of cool water, add salt and pepper.Simmer over a low heat for 15 minutes, mixing from time to time with a wooden spoon. Whiz this mixture in a food processor and then put it back into the pan. Add the broth and cook for a few minutes, mixing. In a bowl, mix the egg yolk with the pecorino.Remove the pan from the heat and pour the egg and cheese stirring. Cook the pappardelle in plenty of boiling salted water, drain al dente and place them in a serving dish, then pour the sauce over it, sprinkle with the leftover parsley and serve.