1 single pie crust (see my Pie Crust 101 tutorial here.)
1 cup bacon, either cubed from slab bacon, or from about 4 thick slices
3 cups leeks from about 3 large leeks, thinly sliced and cleaned
1/4 cup dry white wine
1 teaspoon fresh thyme leaves, or 1/2 teaspoon dry
1 cup gruyere cheese, or cheese of your choice, grated
3 large eggs
1 cup milk
Heat the oven to 375 F.
Prepare the tart dough as described here. Place it in the baking dish and refrigerate until needed.
Over medium heat, brown the bacon. When cooked to your liking, transfer to a plate lined with paper towel. Pour off all but two tablespoons of bacon grease from the pan. (Note: If you’d prefer not to sauté your leeks in the bacon fat, wipe out the pan and use two tablespoons of butter instead.)
Add the leeks and thyme to the warm pan with the bacon fat. Sauté for a few minutes and then add 1/4 cup of water. Allow simmering, stirring occasionally, for about five minutes until the pan is mostly dry. Add the white wine, and allow simmering again for about five minutes until the leeks are tender and the wine has been absorbed. Season to taste with salt.
Scatter half of the grated cheese around the bottom surface of the tart crust. This will provide a nice barrier to keep any moisture from the filling from making the crust soggy. Scatter the leeks and bacon over the cheese. Whisk together the eggs, milk, remaining cheese and a 1/2 teaspoon of salt. Carefully pour into the tart shell, over the leeks, bacon and cheese.
Transfer to the oven and bake at 375 F for about 40 minutes, until the crust and top are golden brown, and the center is firm and no longer wiggles.
Allow to cool slightly before cutting and serve either warm or at room temperature.