Put the butter and 150 ml (1/4 pint) 2/3 cup of the cream in a large saucepan and bring the mixture to the boil over a medium heat. Reduce the heat and then simmer gently for about 1 1/2 minutes, or until slightly thickened.

Meanwhile, bring a large pan of lightly salted water to the boil. Add the fettuccine and olive oil and cook for 2 - 3 minutes, until tender but still firm to the bite. Drain the fettuccine thoroughly and then pour over the cream sauce.

Toss the fettuccine in the sauce over a low heat until thoroughly coated.

Add the remaining cream, the Parmesan cheese and nutmeg to the fettuccine mixture and season to taste with salt and pepper. Toss thoroughly to coat while gently heating through.

Transfer the fettucine mixture to a warm serving plate and garnish with the fresh sprig of parsley. Serve immediately, handing out extra grated Parmesan cheese separately.

This classic Roman dish is often served with the addition of strips of ham and fresh peas. Add 225 g (8 oz) 2 cups shelled cooked peas and 175 g (6 oz) ham strips with the Parmesan cheese in step 4.