Moonstones....

[Nekotee]

You may also want to consider trading them in for Better Crowned Pies. These used to be the best way to level CUL desynth at high levels, and while that's no longer the case, they're still usable for a given level range and may sell for a decent price.

Or, for that matter, you can USE them - they are a food that grants +2 Spiritbind, which is worth considering if you do a lot of spiritbinding for Materia.

Crap someone was faster than me...
Yes either desynth or spiritbond this pie is great ! (or exp !)