I don't know if this is allowed but I've been trying to find a story which I read years ago and can longer find it.
The premise is in a school a lunch lady knocks over an ingredient into some food which doubles the mixture. However someone eats something sugary straight after it will double the ingredient again.
A girl eats a chocolate bar in her classroom and the inflates into a huge ball and is pushed around by her friend.
Any help will be greatly appreciated ☺️
Found it!
http://web.archive.org/web/20111231105735/http://busting-fabric.deviantart.com:80/art/Swelling-Chocolates-And-Love-270779424
Looks like Busting-Fabric's DA account was deactivated somewhere around 2019, and Google doesn't show results for this story anymore. The only way I was able to find it was by searching my DA archive for type:htm chocolate school "lunch lady".