1) Preheat the oven to 190C/375F/Gas 5.
2) To make the shortcrust pastry, put the flour and a pinch of salt into a food processor. Add the butter and lard, and blend to the consistency of fine breadcrumbs.
3) Transfer this to a mixing bowl. (If you don’t have a food-processor, mix the butter and lard into the flour with your fingertips in a mixing bowl until.) Stir in 3-4 tablespoons of cold water – just enough to be able to bring the mixture together into a ball.
4) Turn the dough out onto a lightly floured work surface and knead briefly until smooth.
5) Roll out the pastry to fit a 25cm loose-bottomed flan tin.
6) Press the pastry well into the crease of the tin and prick the pastry base all over with a fork, and place in the fridge to chill for 30 minutes.
7) Line the tart case with baking paper and fill with baking beans. Blind bake for 15 minutes, then remove the beans and paper and return to the oven for a further 10 minutes, or until the base is golden-brown.
8) Remove from the oven and set aside.
9) Meanwhile heat the oil in a large frying pan, add the onions, season with salt and pepper, and cook for 10-15 minutes on a low to medium heat, stirring regularly.
10) To make the filling, beat the eggs with the cream and cheese in a jug or bowl, season.
11) Spoon the onions into the base of the tart case and top with the cheese and cream mixture.
12) Bake in the preheated oven for 30-35 minutes, or until set and lightly browned on top.
13) Remove from the oven and leave to cool slightly.
14) Sprinkle basil leaves over the top before
serving.