1 7/8 c. all purpose flour
9 tbsp. cold unsalted butter
3 tbsp. cold vegetable shortening
3/8 tsp. salt

FILLING:

1 1/2 lbs. onions
3/4 stick (6 tbsp.) butter
1/2 lb. sliced bacon
1 1/2 c. heavy cream
3 egg yolks
1 whole egg
1/2 tsp. salt
Pepper to taste

In a large bowl blend the flour, butter, vegetable shortening and salt until mixture resembles meal. Add 4 1/2 tablespoons ice water, toss mixture until the water is incorporated, and form the dough into a ball. Knead the dough lightly with the heel of the hand against a smooth surface for a few seconds to distribute the fat evenly and reform it into a ball. Dust the dough with flour and chill it, wrapped in wax paper, for 1 hour.

On floured board roll the dough into a circle 15 inches in diameter. Lift the dough over a rolling pin into a 12 inch French shallow false bottomed flan pan with a removable fluted ring and press dough firmly into the pan. Cut off any excess dough with a floured rolling pin. Prick the bottom of the shell with a fork and chill it for 1 hour. Line the shell with wax paper, cover the paper with foil, and fill the foil with raw rice. Bake the shell in the bottom third of a preheated hot oven (400 degrees) for 10-15 minutes, or until it begins to set. Carefully remove the shell from the pan and let it cool on a wire rack.

In a skillet cook the onions, very thinly sliced in the butter over moderately low heat until they are very soft and lightly colored. Drain the onions through a sieve and reserve them. In the skillet lightly saute the bacon, cut into 1/2 inch pieces, until it is crisp. Remove the bacon bits with a slotted spoon, drain them on paper towel and reserve them.

Return the shell to the pan and fill it with the reserved onions and bacon bits. In a bowl combine the cream, egg yolks, the whole egg and salt and add pepper to taste. Pour the custard over the filling and bake the tart in the top third of a preheated moderately hot oven (375 degrees) for 30 minutes, or until it is lightly browned. Remove the tart from the pan and let it cool on a wire rack for 5 minutes.