Preheat the oven to 180 C / 350 F.
Butter a 9 inch tart pan (preferably loose bottomed ).
Roll out the dough on a well floured surface or on a piece of parchment to a circle about 12 inches in diameter
Transfer the rolled out dough to the prepared tart pan.
Press the dough to the bottom of the pan and also press it along the fluted edges.
Using a sharp knife, run it along the entire edge of the tart pan to remove excess or overhanging dough.
With a fork, poke holes all over the bottom.
Place a sheet of foil or parchment over the bottom and fill with rice or beans. Fold the parchment inwards so the edge of the tart is exposed .
Its easier to place the tart shell on a bigger pan or tray . It is more convenient to move in and out of the oven and also may catch any drips or overflow
Bake for 15 minutes , then remove the sheet / foil with the weights and bake for another 10 minutes until the pastry is light brown.
Remove from oven and cool for a few minutes
Spread the cheese over the bottom of the tart case.
Remove the excess water from the onion- bell pepper - mushroom stir fry and fill it into the tart
Pour the custard over the filling. Do not fill right up to the brim as the filling may over flow in the oven.
Return filled tart into oven and bake at 180 C / 350 F for 50 to 55 minutes until the top is lightly browned and the filling looks set
Cool in pan and gently unmould
Serve warm or cold !