1Parboil the broccoli in salted water for 10 minutes. Heat the oil and butter in a skillet, add the onion and cook over low heat, stirring occasionally, for 5 minutes until softened. Drain the broccoli, add to the skillet and mix well. Stir in the cream and simmer gently for 10 minutes. Transfer the mixture to a food processor and process to a purée. Season with salt and pepper to taste. Meanwhile, cook the spaghetti in a large pan of salted boiling water until al dente, then drain, toss with the broccoli and cream mixture, sprinkle with Parmesan and serve.