Mod 80 if the shiur of a kneidal is a k’beitzah then I think we would pasken that shlish mili’bar in which case to be mekayem hiddur mitzvah it would need to have the volume of three modern day eggs.
For those of us that are makpid to have 2 kneidlach in case the first wasn’t eaten within the time limit (ie. tasted kneidle but burned tongue and had to wait longer than shiur for it to cool down), there are special bowl you can buy in the store – my wife says they are called “serving bowls” that are big enough to hold half a dozen eggs plus lukshin and mandel.
BE AWARE: eating this shiur with all it’s chumros outside of a seudah will probably make you have to bentsch (if you are ashkenaz). But who eats chicken soup during the week anyway.