A combination of half and half and whole eggs creates a tender custard for bacon, cheese, and sautéed onions. Use a meltable, shredded, white cheese like Swiss or gruyere for the best custard feel.
Preheat oven to 350°F. Pre-bake frozen pie shell for 40 minutes as directed in my all-butter pie crust recipe.
While the pie shell is baking, whisk the half and half, eggs and white pepper in a bowl or 4-cup measuring cup and set aside.
Fry the bacon in a large skillet over medium heat until browned. Transfer to a paper-towel-lined plate to drain, then slice or break into ½-inch chunks. Reserve 1 tablespoon of the clear, rendered bacon fat, discard the rest, and carefully wipe out the warm skillet.
Add the bacon fat back to the skillet and cook the onion over medium heat for 4-5 minutes or until tender, and set aside.
Once the pie shell has been pre-baked, remove it from the oven, set it aside to cool for a few minutes, and raise the oven temperature to 375°F.
Place your quiche on a sheet pan (I find it's much easier to transfer it in and out of the oven this way, plus the sheet pan helps catch any potential drippage. Scatter the cheese on the pre-baked pie shell then top with the bacon and onion. Slowly pour in the custard mixture over the bacon mixture.
Bake for 30-35 minutes or until the top of the quiche puffs and begins to brown and a cake tester or toothpick comes out clean while the center may still be somewhat jiggly.
Transfer to a cooking rack where the egg will continue to set. Cut into slices and serve warm or at room temperature. If making ahead, bring to room temperature for 15-30 minutes before serving.