Audhumla (Old Norse Auðhumbla, also Audumla, Audumbla and similar) is the primeval cow of the creation of the universe in the Prose Edda. When the icy frost of Ginnungagap melted it formed the cow Audhumla. With milk flowing from her four udders she nourished Ymir. According to the Prose Edda Audhumla fed by licking the salty blocks of ice. After licking theses stones of icy rime or frost the hair of a man appeared that evening. The next day showed the man's head, and on the third day the whole man appeared. His name was Buri, and he was beautiful and big and strong. Thus Audhumla licked the beautiful, big and strong Buri out of the ice. Buri's son Bor is the father of Odin.

From the Prose Edda:

Gangleri asked, ' Where did Ymir live, and what did he live on?'
'Next happened that as the icy rime dripped, the cow called Audhumla was formed. Four rivers of milk ran from her udders, and she nourished Ymir.'
Then Gangleri asked, 'On what did the cow feed?'
High replied, 'She licked the blocks of ice, which were salty. As she licked these stones of icy rime the first day, the hair of a man appeared in the blocks towards the evening. On the second day came the man's head, and on the third day, the whole man. He was called Buri, and he was beautiful, big and strong.

To the right: Audhumla licking Buri from the ice in an Icelandic manuscript by Ólafur Brynjúlfsson from 1760 (Royal Library, Denmark, NKS 1867 4º).

References:
Sturluson, Snorri. The Prose Edda. Translated with an Introduction and Notes by Jesse L. Byock. New York: Penguin Books, 2005.