Pie Day

What the day is

Pie Day is observed on January 23. It is worth saying immediately that this is not Pi Day, the mathematical one, which falls on March 14 because the date reads as 3.14. The two get conflated every year.

Origin and background

Early pies were not really about the pastry. Medieval European cooks baked meat inside a thick flour-and-water casing called a coffin, and its purpose was structural and preservative: it held the filling, sealed it from air during a long bake, and let it be carried and stored. The crust was frequently inedible by design, made hard and thick, and was discarded or given away rather than served.

Pastry became worth eating when fat entered it in quantity, which is also where the useful technique sits. Shortcrust and flaky pastry are the same ingredients treated differently. Rubbing fat thoroughly into flour coats the proteins and blocks gluten, producing a tender, crumbly, uniform crust. Leaving the fat in visible flattened pieces instead creates layers: in the oven the water in those pieces turns to steam and pushes the dough apart, lifting it into flakes. Same bowl, different handling, entirely different result.

Two rules follow from that and explain most failures. Keep everything cold, because fat that melts before baking soaks into the flour rather than staying separate. And handle it as little as possible, because working the dough develops exactly the gluten the fat is there to prevent, which is what makes pastry tough and shrink in the tin.

The soggy bottom is a heat problem rather than a mystery. Blind-baking the base and using a metal tin, which conducts far better than glass or ceramic, deals with most of it.

How to take part

• Keep the butter, the water and ideally the bowl cold.
• Stop mixing while the dough still looks rough and streaky.
• Rest it in the fridge before rolling and again before baking, which prevents shrinking.
• Blind-bake anything with a wet filling.
• Make a savory pie, which is the older form by several centuries.