I have a few theories that i'm trying out. Let me know what you think
I think these trials have a magic number that you need to complete. For the expansion, x numbers of expansion plus the new plot. Most people get it because they've expanded enough.
So, for Chef badge:here's the description "Prepare feasts fit for royal blood?"
Key word: feasts. So you make feasts. What feasts? royal blood. In the kitchen, the "royal sundae" is fit for kings and queens. So answer: sweet feasts. You make 5, 10 or some numbers of sweet feasts.
What do you think?