Heat Control

Why Chawanmushi Gets Holes (Su)

Diluted egg sets near 80C. Above about 90C, its water boils into bubbles. Stay in the gap between.

Core Concept

Custard has a safe window between setting and boiling. Holes appear when the water inside boils. Gentle steam keeps it in the window.

Did You Know?

Su means a nest in Japanese. Cooks say the custard has a nest when it fills with holes.

The custard sets before it boils

Egg diluted with dashi sets at about 80C. That is well below boiling. So there is a window between set and boil.

Above the window, water turns to steam

Chawanmushi is mostly water. Above about 90C, that water starts to boil. Tiny steam bubbles form inside the soft custard. The egg sets around them and locks them in.

Holes also cost you juice

Each hole pushes dashi out. The custard turns spongy and weeps liquid. The smooth texture is gone for good.

Three ways to stay in the window

Use the lowest heat. Leave a small gap under the lid. Keep the cups off the direct boil of the water.

Shunta says:

I tilt one cup after 12 minutes. If the center wobbles like jelly, it needs a little more.

🛠 Cause & Solution Matrix

❌ Symptom	🔍 Cause	💡 Solution
Small holes all through the custard	The steam was too hot	Lower the heat and open a gap under the lid
Dents on the smooth top	Water dripped from the lid	Wrap the lid in a towel
Grainy spots in the custard	The dashi was hot when mixed	Cool the dashi below 40C first