"Man In An Ice Cream Parlor, A" joke

A man was in an ice cream parlor waiting to buy some ice cream. There was one lady in front of him. She ordered a chocolate cone.
The soda-jerk told her he's sorry but they have run out of chocolate. She said, " OK, then I'll have some chocolate."
He told her, " Lady, I'm out of chocolate."
Once again she said, " OK, I'll just have some chocolate."
Exasperated, he said, " Lady, spell VAN as in vanilla."
She spelled van.
He said, " Good, now spell STRAW as in strawberry."
She spelled straw.
He said, " Good, now spell FUCK as in chocolate."
The lady said, " There is no fuck in chocolate."
He replied, "That's what I'm trying to tell you."