• Heat the oven to 425°F (220°C) mark 7.
• to make the pastry
• Sift the flour into a bowl, cut the margarine and lard into small pieces and rub into the flour with the fingertips until the mixture resembles fine breadcrumbs.
• Add sufficient water and work in with a knife to make a firm dough. Line a shallow round 9 in. (22.5cm) tin with the pastry and chill in the refrigerator for 10 minutes.
• Cover with crumpled foil or greaseproof paper and baking beans and bake blind for 15 minutes.

to prepare the filling

• Melt the butter in a small saucepan, add the onions and bacon and fry gently for 5 minutes.
• Remove the flan from the oven and take out the beans and paper.
• Lift the onion and bacon from the pan with a slotted spoon, drain well and spread over the base of the flan.
• Blend the eggs with the cream, salt and freshly ground pepper, pour into the flan and sprinkle with cheese.
• Reduce the heat to 350°F (180°C) mark 4 and continue cooking for a further 25-30 minutes or until the filling is set and golden brown.