Typical quiches suffer from one of several classic flaws. Some feel so slight on the plate they’re more tart than main-course material, while others are so overaccessorized with add-ins that the carefully bound egg-cream mixture either breaks into a curdled puddle or fades into the background.
We wanted a streamlined version of the ultimate quiche: thick-crusted and brimming with creamy custard in which a healthy dose of fillings-the bacon, onion, and shredded Gruyère of the classic Lorraine version-was perfectly suspended.
To accommodate extra filling, we opted for a 9 by 2-inch round cake pan, which closely approximated the ring mold used in our favorite test recipe. For added insurance against leaks and tearing of the crust, we employed three tricks. First, we lined the pan with a foil “sling” to help lift the pastry from its mold. Second, we picked up a handy pastry technique from our favorite research recipe: Using most of a double-crust pastry, we rolled out a 15-inch round and draped a generous amount of dough up and over the sides of the pan, which helped to anchor the crust in place, preventing it from sagging or shrinking when prebaked. And third, we glazed the baked crust with an egg white wash before adding the filling, which helped seal any would-be cracks.
The success of a delicate custard depends on just the right ratio of eggs to liquid-including any excess moisture exuded by our filling’s watery ingredients, like onions-plus gentle, even heat. Too few eggs left the custard loose and runny, while too many lent it a scrambled-egg flavor and rubbery chew. We found that the best combination included whole eggs, plus the extra yolk left over from sealing the crust, and some dairy (we used equal amounts of whole milk and heavy cream).
Finally, to add the fillings without affecting our perfectly quivering, barely set custard, we whisked a little cornstarch into the dairy component of our custard. This kept it glossy and rich from one edge of the pastry to the other. Better yet, it allowed us to bake the quiche longer, which resulted in a slightly firmer custard that could be sliced cleanly on the day it was baked.