Frozen pastry needs different handling depending on the type: some go straight into the oven with no thawing, while others need a slow thaw in the fridge first. The difference comes down to the dough's structure and how its fat behaves under heat.
Which products can go straight into the oven?
Shaped, frozen pastry dough and cookie dough usually go into the oven unthawed; they thaw and bake at the same time, the only difference being a few extra minutes added to the baking time given in the recipe. Filo and puff-pastry-based pies work the same way, since the whole point of that dough is for the layers to separate and puff up under sudden heat — a pre-thawed puff pastry gives noticeably less lift.
Ready-made pizza dough is usually the exception: it's nearly impossible to stretch while frozen solid, so it needs a few hours in the fridge, or a short stretch at room temperature, until it's pliable enough to work with.
Why is a slow fridge thaw preferred?
For bread dough or shaped yeasted products, a slow thaw in the fridge is preferred, since a sudden jump in temperature can sweat the outside while the inside stays frozen. A slowly thawed dough reaches a more even consistency and bakes up more uniformly; thawing quickly at room temperature can let the outer surface start fermenting early while the centre lags behind.
What should you watch for with buttery doughs?
With laminated, buttery doughs — croissant dough, for instance — leaving them too long at room temperature during thawing lets the butter inside start melting, and the layers blend together; that cuts down on the flakiness and rise you'd expect in the oven. That's why these doughs are either thawed briefly somewhere cool, or baked from fully frozen in a slightly pre-heated oven, so the butter never gets the chance to melt early.
Should the oven temperature change for a frozen product?
For anything going into the oven straight from frozen, the oven needs to be fully preheated to the temperature the recipe calls for; putting frozen dough into a half-warm oven can leave the outside baked while the inside is still frozen. Some recipes suggest running the oven 10-15 degrees hotter for the first few minutes with frozen product, then dropping back to the normal temperature — that helps the outer surface catch up with the slower-heating centre. If the top starts browning too fast near the end of baking, that can be a sign the inside still isn't done, so it's worth checking the centre with a fork.