Jiang Weijin is Jiang Chengde's son, surely he has worked as a chef or assistant chef in Taifeng Building. Because he's not very good at making Mixed Fruit Filling, he created a Mixed Fruit Filling with a very rich recipe using ingredients he's familiar with.
Also because he's not very good at it, he basically doesn't do it.
As for why people like Huang Shengli thought there was nothing wrong and found Jiang Weijin's Mixed Fruit Filling snacks particularly delicious, it's entirely because Jiang Weijin's skill level is high enough. Just like Jiang Weiming, his inventive snacks are still delicious.
If the filling of the mixed fruit filling glutinous rice ball that Gong Liang wanted to eat was made like this, then Qin Huai roughly knew how to try.
Just try randomly.
Qin Huai is very good at this method of researching dishes.
Free to play, trying however he wished.
