The custard can go from being like a solid ball...
What’s happening
This happens because of what custard is made of.
Custard powder is really just cornflour, colour and flavouring (invented by Mr Bird after he found his wife was allergic to eggs so she could not eat egg custard).
Cornflour is very finely ground flour. One of the strange results of the fine grinding is that the particles made will link together if you put a bit of pressure on them, but will immediately separate when the pressure stops.
..to all stringy like this in seconds.
As long as you keep squeezing, those links join together and the custard stays in a ball.
In the same way, the pressure of the spoon handle causes a clean cut to form in the custard, but as soon as it passes, the custard becomes liquid again.
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