Oil is the answer to sticky dumplings.

A quick toss in oil before packing is the simplest way to keep dumplings from gluing themselves together in a lunch box.

The why: dumplings stick because starch. When they cool, surface moisture and starch turn into glue. Anything wet that sits against them does the same thing. Oil breaks that seal.

The how: after cooking, give them two or three minutes on a plate so the steam stops rising. Steam is moisture, and moisture is enemy number one. Then toss them in a tiny bit of oil — sesame oil adds flavor, a neutral oil like canola is invisible. The oil film does the work.

If you’re stacking layers, add parchment paper or a lettuce leaf between them. And keep dipping sauce in a separate container. Sauce right on the dumplings washes the oil film off and gives the starch its glue back.

Five seconds of oil beats prying apart a dumpling with a fork at your desk.