Pre-baking, also known as par-baking, also known as blind-baking is a common technique among tart bakers, especially when they’re planning to employ an especially dense and/or wet filling. The idea is to bake the crust through before it becomes sodden and won’t bake up at all (think pumpkin pie). The crust is inserted into a rather hot oven (375 or so) for between ten and twenty minutes, held down with “pie” weights (since even an unleavened dough will bubble up and blister due to the action of steam).
It’s a great idea, however it creates a potential hazard of its own: of over-baking the crust, especially at the rim. Thus, the best way to pre-bake a crust is to enclose it entirely in foil as I shall now demonstrate. Begin by applying a thorough coating of non-stick cooking spray to a sheet of tin foil:
Gently press the sheet — slick side down — into your well-refrigerated (ideally frozen) tart crust.
Curl the excess over the rim of the tart or pie pan to completely enclose the crust. What good will this do? Well, you know how shiny metal surfaces reflect light? They reflect heat just as well.
Line the foil-covered pan with ceramic pie weights if you like. Some people use dried beans. I myself am a loose change man.
Most recipes recommend pre-baking a crust until it’s lightly browned. Personally, I think that’s too much. I suggest baking only until the crust feels firm, but is still very pale in color (usually around 12 minutes for most 9-inch or 10-inch pie or tart crusts). Assuming the tart will be in the oven at least twenty minutes or more, you can leave the browning for the main bake.
Of course, not every pre-baked tart crust is destined for another baking. Pastry cream-filled fruit tarts, for example. In that case, you want to bake until about this level of doneness:
When the crust is finished, gently — oh, so gently — gather up the aluminum foil with the weights inside. A film of crust from the center of the shell will likely stick to it, but if you’ve lubricated it well, nothing more. To finish off the shell (if you’re not going to bake it with a filling), return it to the oven for five more minutes until the bottom surface is very lightly browned.