I was baking a cake when I saw some egg shell in the mix. I said, "You've got to be yolking me!"
You've Got To Be Yolking
Explanation
Explain Bear
Okay, so listen up, you donut. The joke is a pun. "Yolking" sounds like "joking." The dude found egg shell in his cake mix, so he's saying, "You gotta be kidding me!" but using the word "yolking" because it's about eggs. Get it now, butterfingers?