The Health and Mana on consumption effect only occurs when you begin 'using' a potion-- if you queue up multiple Biscuits, you will only get the 20HP/10MP effect when the last tick of the previous one ends.
Total Biscuit of Rejuvenation is an item in League of Legends. This item is not available for purchase. Champions will begin a match with this item in their inventory if they invested a point in the Biscuiteermastery.
Because this item is technically different from Health Potion and Mana Potion, it will not queue up when used simultaneously with those.
This allows a one-time quick regeneration early game.
This item is named after John Bain aka TotalBiscuit, The Cynical Brit a famous YouTuber and game commentator, for achieving a high number of LoL referrals. His original intent, as stated in one of his videos, was for the item that was to be named after him be a top hat.
Having the related mastery point for the item gives the related additional item Poro-Snax in the Howling Abyss map that can be used, as the name suggests, to feed Poros.