Fondant au Chocolat

There's an event upcoming that will have Divine enemies, so Fondant will be useful then.

It is certainly a useful ce, but not as universally useful as Golden sumo or hns. I would make sure that you at least get one copy of the CE and pick up the rest if you have time by the end of the event. This event is a long one and it's easy to farm so you might be able to.

And remember the quests drop both CE's so you may get some freebies while farming. I got one of each to drop already.

Personally, I wanted at least 2 or 3 of these just to farm chocos, since I considered the Valentine CEs to be a complete waste of time, and since it unconstrains my choice of team. It's not far from there to MLBing it, and I was lucky to get a drop as well. It was also the best CE to use for the last main mission, as it gave +10 to the 5 types of drops as I did get them all by then.

I'd say it's worth MLB'ing it just for itself. But I won't MLB the other (Sweet Crystal), though I do plan on getting one copy.

Don't worry so much about the 50% NP, the biggest reason it's useful is the permanent boost to a servant's damage versus Divine enemies and there's basically no other CE that does that. There's Divine enemies scattered across the entire cast and most of them are fairly scary when they show up in more challenging content. There's also a few specific bosses that Fondant is directly optimal for.