I think there’s something in this idea. Kinda Ratatouille-esque.

Couple of pointers:

The protagonist shouldn’t do anything accidentally in order to achieve the goal. A PROtagonist should be PROactive.

How do you create a secret menu anyway? Do the customers get this menu privately and then she cooks them the food without her family knowing? Is this the charade that she’s trying to keep up?

I would remove “accidentally”, explain specifically what she is doing regarding the menu and the food – simpler the better, tell us why what she’s doing is going to help (she creates unusual combos the crowds go wild for?) and somehow explain why she has to do all of this without her family knowing. It sounds a lot but I think once you unpack the story I think it’ll fall into place.

Try the generator too… it might be a useful tool.

Hope this helps.

…and then what happens?

This is just the set up really.

Saying “become dinner guests” suggests that it wasn’t a choice they made. More they were forced into it. Do they know he’s a vampire?

Does it make a difference that this is set in New Orleans?

I think all the elements need to tie up, the murders need to be connected to the aristocrat in someway. There needs to be a reason why they go to dinner. What does the secret society do? How is that connected to the murders?

When a series of brutal murders is linked to a local aristocrat’s secret society, a cynical detective and his cocky partner must follow the clues into a dark and mysterious underworld that’s corrupting the whole community.?

Not perfect at all but you I feel like it has more of the required elements.

The inclusion of the vampire bit really depends where the reveal is that he’s a vampire. If it’s at the end of Act I, then I would include it. If it’s Act II climax, then I wouldn’t. If it’s a midpoint, I would throw a MPR into this logline. Change the stakes… (pun intended).

Hope this helps.