“Whatever melts your butter”

“Whatever melts your butter” means “whatever makes you happy” or “whatever’s your choice/desire” or “whatever’s your flavor” or “whatever turns you on” or “whatever floats your boat.” The silly saying is cited in print from at least 1975.
 
Similar food-related phrases include “Whatever butters your biscuit” (since 1996), “Whatever bakes your cake” (since 1997), “Whatever tickles your pickle” (since 1998) and “Whatever sprinkles your donut” (since 2012).
   
   
Google News Archive
26 September 1975, St. Petersburg (FL) Evening Independent, “Jimmy Dean” by Jim Moorhead, pg. 1B, col. 4:
...(“I don’t know why, I just figure, ‘Well, whatever melts your butter’”)...
     
Google Books
Stereo Review
v. 47 - 1982
Pg. 116:
Whatever, but it quickly degenerates into a laundry list: pops your corn, mows your lawn, melts your butter, etc.
 
Google Books
6 April 1987, New York magazine, pg. 94, col. 3:
But they form a real ensemble in an endearing play (Steel Magnolias by Robert Harling—ed.); you may find that, in Truvy’s phrase, it melts your butter.
   
Google Books
Eden
By Penny Richards
Toronto: Harlequin Books
1993, ©1989
Pg. 105:
“Well, as Seth would say, ‘Whatever melts your butter.’ Ted’s a grown man and he deserves to be happy.”
 
13 May 1994, Syracuse (NY) Post-Standard, “You Can Call It ‘Feb-roo-ary,’ You Can Call It ‘Feb-you-ary’” by Lydel Sims, pg. D8, col. 1:
And ere the diehards launch their attacks, let me add that I’m only giving a personal opinion; “roo” all you please if that’s, as they say, what melts your butter.
   
Google Books
Biggie and the Meddlesome Mailman
By Nancy Bell
New York, NY: St. Martin’s Minotaur
1999
Pg. 31:
“Whatever melts your butter,” she said.