Line a deep 23 cm (9 in) tart tin with the pastry and pre-bake or bake blind.

Pre-heat the oven to 190°C (375°F) Gas 5. Place a baking sheet in the oven to get hot.

Trim the leeks by cutting off their tougher green tops and their root base. Cut into 5mm (1/4 in) slices and wash thoroughly, then drain in a colander or large sieve.

Melt the butter in a large heavy-bottomed frying pan. Add the leeks and fry gently until they start to go slightly soft, stirring occasionally.

Break up the mushrooms into rough pieces, add to the leeks and cook for a few more minutes, stirring occasionally. Add the tarragon and cook for a further 1 minute.

Meanwhile, put the cream cheese into a large bowl and whisk until smooth, then add the cream, eggs, mustard, nutmeg and salt and pepper and mix well.

Place the leek and mushroom mixture into the pre-baked pastry case and pour the cheese mixture over the top. Place the tart on the hot baking tray and bake in the oven for 35 - 40 minutes until it looks set.

Serve with a green salad or a green vegetable, such as sugar-snap peas or broccoli. COOK'S TIP - This tart will serve 10 - 12 as a starter.