Cook the spaghetti. At the same time, heat the oil in a heavy-bottomed saucepan and sauté the onion and garlic for 1 minute. Add the carrot and courgette; sauté, stirring occasionally, for 2–3 minutes. Blanch the cauliflower in lightly salted boiling water for 5 minutes, or steam until tender. Add the crème fraiche, stock and peas to the carrot and courgette mix. Cook for 2–3 minutes then stir in the Parmesan. Drain the spaghetti and toss with the sauce.