If another mod makes mushroom stew stackable beyond 1, attempting to breed a snail with a stack of multiple mushroom stew with replace the whole stack with a single empty bowl

Do you have any examples of mods that do that so I can test with them?

The mod I was using was Charm https://www.curseforge.com/minecraft/mc-mods/charm

(You can also use commands to create stacked mushroom stew but it is apparently vanilla behavior that players eating stacked mushroom stew also consume the whole stack, and that's something Charm fixes)

Fixed.