Why did my puff pastry not rise?

How puff rises in the first place

Puff pastry is hundreds of alternating layers of dough and butter, built by lamination. In a hot oven the butter melts and its water turns to steam, forcing the layers apart before the dough sets. Everything that stops puff rising interferes with one link in that chain: cold fat, sudden heat, or intact layers.

The usual suspects

Work through these in order, because the first two account for most flat pastry.

• Oven too cool: puff needs 200C (400F) or hotter, fully preheated, so the steam arrives before the butter simply melts out
• Pastry too warm going in: soft butter leaks instead of steaming, so chill the assembled pie for 15 to 20 minutes first
• Egg wash on the cut edges: glaze dripping down the sides welds the layers, so brush the top only
• Crushed edges: pressing or crimping too hard seals layers shut, and a blunt knife drags them together when cutting shapes
• Too much rerolling: scraps rerolled repeatedly lose their layer structure and bake up as a dense biscuit
• Wet filling contact: steam from a hot or sloppy filling soaks the underside so it cannot crisp

Rescues and next time

A pie already in the oven with a pale, flat lid can sometimes be saved by raising the temperature to 220C (425F) for the last ten minutes, which at least crisps and colours what rise there is.

Next time, cut pastry with a single sharp downstroke, transfer the lid cold, and bake on a preheated tray. If your oven runs cool, and many do, an oven thermometer costs little and answers the question permanently.

Note that rough puff and all-butter shop pastry rise less dramatically than full puff by design, so compare like with like before blaming your oven. A rough puff lid that flakes and crisps has done its job even without a tall rise.