Pleating dumplings

How to tell it is going right

• The seam is closed along its whole length with no gap at either end of the pleat run: hold one up to the light and no filling shows through the join. A dumpling that opens in the water was sealed against a wet or floured rim.
• The rim is clean and dry where it meets itself. Filling smeared onto the sealing edge is the single most common cause of a burst, and it cannot be wiped off once the dough has taken it up.
• The pleats are even in size and count across the batch, so every piece holds the same weight of filling and cooks in the same time. A tray that ranges from eight folds to eighteen will not finish together.
• The wrapper is thicker at the centre than at the rim, so the base carries the filling without tearing while the pleated edge stays fine enough to eat. A disc rolled evenly flat splits at the bottom.
• It stands up on its own base without slumping, and the pleats still read as pleats after cooking rather than having relaxed into a smooth seam.

Where it goes wrong The rim was wet, floured or smeared with filling, so the seal never took: the dumpling opens in the pot, the filling leaves, and what surfaces is a slack empty wrapper in cloudy water. Uneven pleat counts across a tray compound it, because the batch stops finishing at the same moment.