Q: One of my lovely readers has a question to ask to kick off this new "What went wrong" series. Pat emailed me with a question regarding her failed sour cream pastry; the pastry shrunk in the oven. Why does this happen, and how can she prevent it from happening in future?
A: So much can go wrong with shortcrust pastries! Pastry shrinks because the liquid component of the pastry (in this case, the sour cream, and the fat in the butter) evaporates as you bake it. Obviously, it is inevitable, but there are steps you can take to minimise shrinkage.
1. Firstly, don't overstretch the pastry when you are kneading it out/shaping your dough. Obviously, the thinner your pastry is, the higher the shrinkage.
2. Leave a bit of overhang on your pastry and then let it rest. This way, any shrinkage is accounted for (by the overhang), and the resting actually allows for any liquid to spread out in the pastry dough. This ensures a more consistent result at the end.
3. Finally, bake with an overhang, and when it comes out of the oven and is still warm, cut the overhang off with a sharp knife. If you leave it till it is cold/use a blunt knife it will be flaky, obviously (being flaky pastry and all!)
If you have any questions regarding something you've cooked and it didn't turn out how you were expecting - I can help! My science-y background means that I love working out the real reason behind a recipe failure - thus determining how to prevent it in future. Leave your question in the comments below (or tweet, or FB) and I'll do my best to work it out!