Blood Eggs
Yes, they’re eggs full of blood. Well, not precisely blood; the xeno-species that lays Blood Eggs is compatible with our ecosystem, but it only vaguely has the same kind of DNA as do terrestrial species. Left alone, a fertilized Blood Egg will produce a ‘chick’ as usual; but unfertilized Blood Eggs produce instead a gloopy red fluid that smells and tastes like human blood, but can be cooked the same way that chicken eggs can. It’s absolutely unsuitable for transfusions, though.
On the other hand, it’s a perfectly good nutritional substitute for anything that lives on human blood, for everything from atomic mutant giant ticks to straight-up vampires (and the vampire thing, honestly, is what most people will care about). About three Blood Eggs will serve as a ‘meal’ for your standard vampire, whether fresh or cooked, and eating them will keep any cravings at bay for all but the most literally diabolic sort of nosferatu. Vampires also find that dishes made with Blood Eggs in them are much easier to ‘digest.’