When steaming, you need to cover it with a layer of plastic wrap and put it in cold water.

Your steaming time is a little too short. Steam over medium heat for about 20 minutes.

If it is not solidified when it comes out of the pot, you can continue to put it in the pot to extend the steaming time

And it is best to pass the mixed egg liquid through a sieve to make the steamed double-skinned milk tender