Before there were marshmallow peeps, there was "hiyoko". It's a traditional japanese confection, usually presented in a pastry, such as this.
This is filled with a sweet lima bean paste, and surrounded in a pastry bun shaped like a baby chick. But they can also come in other types of confection, candy, cookie, chocolate, etc.
Hiyoko has been around for generations, invented by a pastry maker in 1912. It's a reflection of Japan's love affair with nature, finding grace in simplicity, and anything that's cute. That itself (minus the cute part) stems further from Japan's national religion, Shinto Buddhism.
The pastry bun itself has a sweet flavor, similar to that of King's Hawaiian Bread, but not as soft. This is a little more dry.
The sweet lima bean paste inside is eerily similar to that of an egg yolk, in terms of color and consistency, which is interesting considering the baby chick theme. It's just sweet tasting, and tastes nothing like an egg yolk. This paste, however, does include egg yolk as an ingredient.
I've had these before while growing up as a kid, but it's been years since the last time I've had one of these. I think these would actually be tastier with a cream filling, like custard or something.
I bought this at the Mitsuwa Market in San Diego, but I'm sure you can find these at any Mitsuwa Market, and at most Japanese food stores, if not this particular brand, but others too.