Recipe for Knaidlach

Recipe for Knaidlach calls for four eggs

The maid came to the Bais Halevi on Yom Tov and said 

 "My Bal Habusta sent me to the Rov with this Shaila.

She told me to make Knaidlach using three eggs and I 

made it with four eggs. May we eat the Knaidlach?"

The Bais Halevi answered not to eat it in the mean time, 

but to come back again the following day with the same Shaila.

The onlookers were puzzled with both the question and the

answer. 

The Bais Halevi explained, This maid must have been

nervous when asking the Shaila and left out part of the story.

She was probably told to use three eggs because that's all

the eggs they had in the house.The maid knowing the 

recipe calls for four eggs picked up another egg from the 

chicken coop.

.which was laid on Yom Tov (ביצה שנולדה ביו"ט)

He told her to come back the following day because

the fourth egg is not בטל being it is a דבר שיש לו מתירין

after Yom Tov it's not Muktza any more therefore

Bitul doesn't apply and one must wait to eat the knaidlach

till after Yom Tov.

A Rav  not only needs to know the answer but also needs

to know and understand the question (Shaila),