Actually, Zhao Jian had simply misunderstood.
The process of making pastries could be powered by water, but making sugar in bulk was a different matter.
Wang Yue had sugar in his space, and it was more than enough for his own use. But it wouldn't be enough to add to the pastries if he wanted to sell them in large quantities, so he had to find another way to make sugar.
That dark, murky substance was only there to provide energy for the sugar-making equipment. The actual source of the white sugar was rice. The equipment used two enzymes to turn the rice into glucose, which was then converted into sugar.
Wang Yue couldn't possibly teach Zhao Jian all that. It would take too much time, and there was no need.
As for why he'd let Zhao Jian see the entire process, it was really a test, much like the silver. If she couldn't resist temptation, and cared only for the Great Song rather than her master, then even though she was his disciple, he'd have to be wary of her in the future.
Wang Yue wasn't worried that anyone would come and take the equipment. He could use a talisman to appear beside it at any time and put it away.
So when Wang Yue saw that Zhao Jian had misunderstood, he didn't bother correcting her. Instead, he smiled and said, "I have a way to make something that tastes sweet at a lower cost. That means these pastries can be made in large quantities."
Le Shan was thrilled. "If we make pastries like these, they'll sell quickly for sure! I'll go tell my sisters to get ready to start a business."
Seeing that Le Shan was so caught up in the business that she'd forgotten all about studying,