FILLING: Slice onions thinly and layer in large saucepan. Add 1 teaspoon of salt to them and set aside to draw out the water for at least 30 minutes. Add 1/4 cup of oil and 1/2 cup of water. Steam onions until transparent and water is cooked out. Meanwhile, place sliced bacon in a small amount of water in a shallow pan and blanch to remove excess fat. Bacon should be limp. Pour off liquid and coarsely chop. When water is cooked out of onions, add 1 teaspoon of flour and stir to dissolve.
Remove from heat and add 2 egg yolks and cream with the onions. Stir constantly.
PIE PASTRY: Sift flour onto a pastry board, cloth or dough bowl and make a large well in the center. Pound butter to soften slightly or have at room temperature. Place butter, egg yolks, salt and smaller amount of water in the well and work together with the fingertips of one hand until partly mixed. Gradually work in flour, pulling dough into large crumbs using the fingertips of both hands. If the crumbs are dry, sprinkle over a tablespoon of more water. Press dough firmly together - it should be soft, but not sticky. Work on a lightly floured board, pushing dough away with the heel of the hand and gathering it up with a dough scraper until smooth and pliable. Press dough into a ball. Wrap in foil or plastic wrap and chill for 30 minutes.
It can be stored tightly wrapped in the refrigerator for up to 3 days.
DIRECTIONS: Roll pastry to about 1/2 inch thickness in a rectangular shape. Place pastry on an oiled baking sheet. Crimp edges of pastry if desired. Beat an egg yolk with a pinch of salt and brush over the entire pastry. This is called "egg glazing" and helps the filling adhere to the pastry. Pierce pastry with a fork in several places to prevent bubbles from forming while baking.
Spread onion mixture over the pastry and sprinkle the chopped bacon on top. Bake at 300 degrees F. for 10 to 15 minutes or until nicely borwned. Cut into 1 inch squares for hors d''oeuvres. May be made a day ahead and reheated. Wait to cut until after heating if made ahead. May be baked in individual tartlet pans or a pie plate.