Move over butter: Organic non-homogenized milk from grass-fed cows is making a move to be America's new dairy darling.

George Siemon, Organic Valley CEO, told The Wall Street Journal that the organic cooperative's nearly $6 per half-gallon Grassmilk carton is now the best-selling item at Whole Foods stores. But Siemon notes that regular organic milk is still the company's top seller by far, since most stores don't carry the Grassmilk product.

Organic Valley markets three types of grassmilk, all non-homogenized, in whole, 2%, and fat free. The company advertises on the product page that cows are 100% grass-fed (and hay fed), delivering a bigger dose of Omega-3 and conjugated linoleic acid. Grassmilk producers do receive a premium above the standard organic price, but cannot feed soybeans or supplemental grains.