Banana Cream Pie Day

What the day is

Banana Cream Pie Day is observed on March 2. A cream pie differs from a baked custard pie in that the filling is cooked on the stove first and poured into an already baked shell.

Origin and background

That stovetop step contains the trap. Pastry cream is thickened with starch and enriched with egg yolks, and egg yolks contain an enzyme, alpha-amylase, whose job is to break down starch. While the custard is warm that enzyme is perfectly happy cutting apart the starch network you have just built. A custard that looked thick in the pan can be a puddle by evening for precisely this reason.

The fix is temperature. The enzyme is destroyed by heat, but not at the point the custard thickens. The mixture has to reach a full boil and be held there, bubbling, for a minute or so while whisking. Most recipes that fail say to remove it as soon as it coats the spoon, which is exactly too early. Boiling a starch custard feels wrong and is correct.

The bananas bring their own problem, which is browning. Cut surfaces oxidize quickly, and the usual defenses are acid and exclusion of air: a little lemon juice on the slices, and burying them in custard rather than layering them on top.

The banana itself is worth a note. Nearly every banana exported worldwide is a Cavendish, and every Cavendish is a clone, propagated from cuttings rather than seed. It became the standard only because the previous export variety, Gros Michel, was destroyed by a fungal disease in the mid-twentieth century. A related strain now threatens the Cavendish, and a single clonal crop has no genetic variation to resist it.

How to take part

• Boil the pastry cream properly for a minute. This is the whole difference.
• Toss the banana slices in lemon juice and cover them with custard.
• Blind-bake the shell fully, since nothing else will cook it.
• Chill it for several hours before slicing.
• Assemble on the day. It is not a pie that improves overnight.