Outo no Hazure no Renkinjutsushi ~Hazure Shokugyou Datta node, Nonbiri Omise Keiei Shimasu~ - Vol. 4 Ch. 25 - A Gift For The Royal Family

[JJTheWeeb]

The rings stay ON during sex, Doctor's orders

 

[Scruffy]

It is cream puffs.
Though some might get nitpicky about the specifics (like how this one is cut open vs the poke a hole type) the basic is the same.

Cream puffs are made with Choux pastry, hence the name.

 

[Aqua_Mizue]

Thanks for the chapter

 

[Lunasol]

The rings stay ON during sex, Doctor's orders

That is correct. If it wasn't ON, then the effect went OFFLINE.

 

[Hont91]

The heck are you talking about fertility with a child that doesn't even had "the talk" yet? Thankfully the appraisal seems to be the responsible kind that doesn't share unneeded details

 

[Grikath]

it's wild that they asked a child who doesnt even know what sex is to make these for them

Unless you completely isolate a child from any kind of reality, you'll find the kids pick up on the whole "Man + Woman + "married/couple" = babies.." at a really young age.
In fact, it's one of the Classic Uncomfortable Kid Questions... "Where do babies come from?" for the 3-5 Age group....

The actual method of making those babies is generally something they're not interested in... yet..
It's a simple fact that it happens. It's all around them... You get to see most pregnant women in your "formative years" ... Because you are a kid, and are ( or at least used to be...) highly likely to be surrounded by young mothers, of which a fair lot are shooting for another one...

The flavour text also does not state anything other than "promoting blessing with a child". Method unknown... Just that it makes it more likely to Happen...
And that's really all a kid would need to make a "lucky charm" to help someone they like to get a little brother/sister.
Because kids do that kind of stuff. Quite innocently and sincerely. It's the "adults" who get flustered about it....