Some interesting statistics from Google exact search today: (Am I organized?)
A knife through butter ............................3,080 listings
A warm knife through butter .............................. 431
A hot knife through butter .......................... 13,800
A Knife through warm butter ...............................200
A warm knife through warm butter....................................0
A hot knife through warm butter................................126
A knife through hot butter ................................316
A warm knife through hot butter ...................................0
A hot knife through hot butter....................................5
I think people make up their own "idioms" to throw up off.
BMO