Not blind-baking the crust

One common misconception about quiche is that because the filling is baked for a while, the crust and filling can be baked together raw. This would be a huge blunder. Always bake the quiche crust ahead of time. Blind baking refers to the process of baking a pie or tart dough without the filling. What happens if the crust isn't pre-baked? The custard filling will seep into the crust, preventing moisture from escaping. You won't get a crisp crust no matter how long you bake; instead, you'll get that dreaded soggy bottom that bakers fear.

Line your tart shell with parchment paper and fill it with something heavy, such as pie weights or dry beans, to blind bake. This keeps the crust from puffing up while baking. Bake the weighted crust for 20 minutes at 350 F, then remove the weights and bake for another 10 to 15 minutes. Stella Parks suggests using granulated sugar as the pie weight if you don't have any weights on hand. The sugar can even be reused three or four times. Parks observes that the sugar will develop a nice toasty flavor, which is ideal for desserts such as meringues.