“How do you cook duck eggs?”/“You quack them open.”

“Quack” sounds a little like “crack,” and a pun about duck eggs has been made since at least 2004. “How do ducks eat hardboiled eggs? They quack them!” was posted on Twitter on January 7, 2012.
 
A riddle was posted on Reddit—Jokes on March 26, 2018:
 
Q: How do you cook duck eggs?
A: You quack them open.
         
 
19 March 2004, Florida Today (Melbourne, FL), “Help” by Doug Lang, pg. 3:
No ducking this egg query
(...)
Columnists find it hard to resist saying: “Be careful not to quack them!”
 
Twitter
Owlkids Publishing
@owlkids
How do ducks eat hardboiled eggs? They quack them! #MishMash #chickaDEE
1:55 PM - 7 Jan 2012
 
Twitter
Andy Campbell
@SirAndyCampbell
Mom: Would you like eggs for breakfast?
Kid: Only if you quack them for me!
#JokeOfTheDay
9:16 AM - 14 Aug 2012
   
Twitter
Brett Gordon
@MrBrettGordon
Q: How do geese open eggs?
A: They quack them open. #OriginalJoke 🐣
2:48 PM - 6 Jul 2015
   
Twitter
Cristina aka tina
@tinaa_cx
How do ducks cook their eggs ?
They QUACK them 😂😂
5:13 PM - 23 Oct 2016
   
Twitter
Brooke
@brookeeickert12
Riley: “what do you even do with duck eggs?”
Dad: “you QUACK them!”
5:22 PM - 7 Apr 2017
 
Reddit—Jokes
How do you cook duck eggs?
submitted March 26, 2018 by lvest
You quack them open.
COMMENTS
NightStriderXP
Balut is one duck egg dish where you cook them while they are still in the egg.