To make the pastry, sift the flour, salt and mustard powder into
a bowl.
Rub in the margarine and cheese until the mixture forms soft
breadcrumbs.
Add 30 ml or 2 tbsp water and bring together into a ball.
Chill, covered or wrapped, for 30 minutes.
Meanwhile, make the filling: melt the butter in a pan, add the
onion and cook gently for 10 minutes, stirring occasionally, until
softened but not browned.
Stir in the apple and cook for 2 - 3 minutes.
Leave to cool.
Roll out the pastry and line a lightly greased 20 cm or 8 in
spring form tin.
Chill for 20 minutes.
Preheat the oven to 200oC/400oF/Gas 6.
Line the pastry with greaseproof paper and fill with baking
beans.
Bake blind for 20 minutes.
Beat together the eggs, cream, herbs, seasoning and mustard.
Grate three quarters of the cheese and stir into the egg
mixture, then slice the remaining cheese and set aside.
When the pastry is cooked, remove the paper and beans and pour
in the egg mixture.
Arrange the sliced cheese over the top.
Reduce the oven temperature to 190oC/375oF/Gas
5.
Return the tart to the oven and cook for a further 20 minutes,
until the filling is golden and just firm.
Serve hot or warm.
Serves 4 - 6
Cooking Tip :
You could substitute other hard cheeses, such as Cheddar, Lancashire, or
Red Leicester for the Gruyére, if you prefer.
