The Bannered Mare in Whiterun, on a shelf in the kitchen. It can be stolen or simply taken if the innkeeper is a friend. It does not appear until after the quest 'Argonian Ale Extraction' has been started.
It is the quest item for the quest 'Argonian Ale Extraction' given by the beggar Brenuin in Whiterun.
You only need to have had the item in your inventory for the replica recipe to be unlocked.
Made at the Distilling Station in the Wine Cellar with the following materials:
The Bannered Mare in Whiterun