Why do you Need to Pre-Bake a Pie Crust?

What is blind baking?

Blind baking is another term for pre-baking, and simply means to cook a pie crust or pastry cake by itself, without the filling. For some recipes the pastry is entirely blind baked, while for others the filling may be added part way through.

Blind-baked pastry often has oven-proof pie weights placed inside to mimic the weight of the filling, holding the pastry in place and preventing it from shrinking away from the edges of the tin. It may also be pricked several times with a fork to prevent bubbles from forming.

Why do you need to do it?

Blind baking is a good idea for several reasons. Firstly, many fillings don’t require cooking for as long as their pastry cases. Many fruit fillings, for example, will reduce down to mush in the amount of time it takes to properly cook their pastry casings, while pumpkin pie filling can dry out and start cracking if left in the oven for too long.

Instead of choosing between raw pastry on the one hand and mushy filling on the other, it makes sense to start cooking your pastry first then add the filling later, so they’re both cooked for the perfect amount of time. Some pie fillings - fruit tarts for example - don’t need cooking at all, in which case you will need to fully blind bake the pastry before adding the filling.

In fact, even if your pastry and filling do need roughly the same amount of time in the oven, it can still be a good idea to blind bake the pastry for a short while first. Putting wet filling directly onto raw dough can weaken the structure of the pie, as the dough will soak up all the moisture, making it weak and floppy.

The filling will also give off steam as it cooks, which can weaken the pastry even more, leading to the dreaded soggy bottom. In some cases the dough will split, causing the filling to seep out and burn onto the outside of the crust. 

How to blind bake

For crisp, golden-brown pastry, without a soggy bottom in sight, follow our simple, step-by-step guide to blind baking.

1. Pre-heat your oven to 425°F and place one of the racks just below the centre position, so the pie itself will be right in the middle of the oven.
2. Line a pie tin with pastry, trimming off the excess and crimping the edges.
3. Take a large piece of parchment paper or foil and lay it over the pastry, making sure it is well pressed up against the bottom and sides of the tin.
4. Add in your pie weights, again making sure they are tightly packed against the bottom and sides.
5. Place the dish in the oven and bake for 12 to 15 minutes, or until the edges have just started to turn golden brown. 
6. Remove the dish from the oven and take the parchment paper or foil by the corners, lifting both it and the weights out of the tin. 
7. At this point, the edges of the pie should look almost cooked, while the bottom will look raw and wet. Return to the oven and cook for another 5 minutes, or until the bottom dries out.
8. Check your recipe. You may need to add the filling at this point and continue cooking. If your filling is uncooked, continue blind-baking the pastry for another 5 minutes, until the edges are browned and the bottom is slightly golden.
9. Remove from the oven again and assemble the pie according to your recipe.

Pie weights vs. docking

When you blind bake a pastry case, it has no filling to hold it in place, which makes it more likely to shrink away from the edges of the tin. It may also form unsightly bubbles and wrinkles, as the steam from melting fat can get in between different layers of pastry, making it puff up and deflate quickly. 

There are a couple of techniques used during blind baking to counter these problems. The first is using pie weights, which we have already briefly mentioned. These come in a variety of different forms, from ceramic pebbles to chains made of metal discs, and you can improvise homemade versions using beans, rice or sugar. They act as a dummy filling, holding the pastry case in place so it doesn’t shrink away from the sides, and pressing down on it so it doesn’t inflate.

Another way to prevent bubbling is to prick the pastry all over with a fork before cooking it, a process sometimes known as ‘docking’. This creates an escape route for any steam that may get into the pastry, so it shouldn’t build up and form bubbles. Docking is only necessary when blind baking, as the weight of the filling is enough to stop the pastry from inflating, and there is more risk of juices seeping through the crust if you make lots of holes in it.

Tips and tricks

Make sure you have enough weights

To hold your pastry in place both on the bottom and at the sides, it needs to be filled almost to the top with pie weights. Frustratingly, pie weights are often sold in rather small quantities, so you may need to buy a few to properly fill your pie.

Protect your edges

If you’re using pie weights, the edges of your pie are likely to be the only part that is not covered either by parchment or foil, or by the tin itself. This means that they are likely to cook a little more quickly than the rest of the pastry, and while nicely-browned edges are a wonderful thing, you may sometimes find that they start to burn while you’re waiting for the bottom to cook. 

To prevent this, you can buy metal crust shields to fit over the edges, deflecting heat away from them while the rest of the pie finishes cooking. You can even fashion your own using aluminium foil if you don’t have the room or the budget for more baking tools.

Repairing holes 

Despite your best intentions, sometimes the occasional hole or crack will appear in the pastry after blind baking. But don’t panic, these can easily be fixed. Just make sure you keep your pastry offcuts when trimming off the edges, and use small pieces to plug the holes. You can also brush the pastry with slightly beaten egg white to fill in any invisible holes and form a protective layer between the pastry and the filling. After making your repairs, return the pie to the oven for 5 to 10 minutes to cook the raw pastry and the egg white.