The egg in that box is real, but later he secretly changed the egg in his left hand (if you look closely, you will find that his left hand is very tight). As for how to change the egg, there are props on Taobao. Then he (the props are half an egg, sticky, and can be firmly attached to the real egg, and the props are well made, so you can't tell if you don't look carefully) sticks the props to the real egg and thinks of a heart. There is a real yolk and some real egg whites in that half egg. Those people were careful to check and were afraid of breaking the egg, so they didn't break the middle of the "heart egg" hard. The heart-shaped part in the middle was very sticky.

After that, two yolks appeared when the "heart egg" was broken, and then the evidence disappeared.