Preheat the oven to 190C and line and grease a 24 cm tart tin with a removable base.
Roll out the pastry to 1/8 inch thick and line the tart tin.
Place in the refrigerator to rest for 10 minutes, prior to baking.
Remove the tart tin from the refrigerator, cover the pastry case with a round of wax paper and fill with baking beans.
Bake for 15 minutes at 190C.
Remove the baking beans and wax paper and return to the oven for 5 minutes to cook the base.
While the tart is cooking, slice the courgettes and fry them in the olive oil until lightly browned, do not overcook them.
Season with salt and pepper and set aside.
Place the melted butter in a pan, add the flour, stir well and cook for 2 minutes.
Remove from the heat and gradually stir in the milk making sure there are no lumps.
Return the pan to the heat and cook until the mixture thickens.
Add the chilli powder and the mace and season to taste.
Set aside to cool slightly.
Strain the courgettes and tip them onto a piece of kitchen paper to remove any excess water. Cut the parma ham into strips and drape it across the bottom of the pastry case.
Sprinkle the courgettes on top of the ham, reserving a few for decoration.
Lightly beat the egg yolks and stir into the mixture, add the cheese and whisk until thick and glossy.
In a separate bowl whisk the egg whites until stiff.
Gently fold the egg whites into the cheese mixture a little at a time, being careful not to lose all the air in the egg whites.
Spoon the mixture on top of the courgettes, place the reserved slices on top and sprinkle liberally with the grated parmesan.
Bake in the centre of the oven for 35 – 40 minutes until the tart is golden brown.