Butter face?

I have a student, a senior named DJ, who was interested in whether the new season of Survivor began tonight. We checked the internet and found that, indeed, it does. He was surveying the panoply of ladies and noticed one in particular.

"She's got a Butter Face," he stated.

"A what?"

"A Butter Face."

I was a little hesistant to ask. "DJ, what's a Butter Face?"

"Oh, you know. She's got a really nice body, Butter Face..." he cackled uncontrollably.