Chocolate was a symbol of how bad Sandy and Tom’s marriage had become.
They were in a drive-thru ordering food, and Sandy asked for a chocolate shake. Tom said “no” and forced her to reorder. Vanilla, he believed, was the better choice. He was convinced chocolate would make her face break out and cause her to gain weight.
Tom didn’t realize it at the time, but the problem wasn’t chocolate, it was control. To get the marriage he was after, Tom thought he had to rule with an iron fist.