Any time I’ve suggested a tool, a piece of equipment, or a culinary term that’s unfamiliar to you, you can go to Learn to Cook for more information.
After cooking the bacon, drain out the fat, but don’t wash the skillet. Melt the butter or heat the oil in the skillet used to cook the bacon, over medium heat. When the fat is hot and bubbling, add the leeks and cook them until softened, very fragrant and have picked up any remnants of bacon flavor from the bottom of the pan. Season with salt and pepper and remove leeks to a bowl, so they can cool.
Place a shallow baking sheet on the center shelf of the oven. Preheat the oven to 375 degrees. Stir the egg yolk in a small cup with the Dijon mustard. * With a pastry brush, brush the interior of the partially baked (totally cooled) pie shell with some of the yolk to seal the crust (see note below.)
* This procedure is called “water-proofing” and is an optional step.) With sweet crusts for fruit tarts, etc., you would use an appropriate flavor of melted jelly or strained preserves.)
Pour the cream into a large measuring cup (with a spout) and stir in the beaten eggs. Add salt, black pepper and either a few gratings of fresh nutmeg or a few shots of your favorite hot sauce. Scatter cubed or shredded cheese on the bottom of the partially pre-baked deep dish pie crust, reserving a small handful, for the top. Scatter the cooked bacon on top of the cheese, and then place the sautéed leeks on top of the bacon. Pour the cream mixture over the filling ingredients and then scatter the reserved cheese over the top. Arrange the tomatoes decoratively around the inside border of the pan and then place the dish on the baking sheet in the preheated oven. Bake the quiche for 45 to 55 minutes or until the filling is set (but wiggles ever so slightly) and the top is turning golden (a short paring knife should come out clean, when inserted into the top center). Remove the quiche from the oven and let the quiche settle on a wire rack for 10 minutes, before slicing. This quiche may be made early in the day and reheated in a 350 degree oven. Serve hot or warm.