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 15 health / 15 mana 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 previously gave the related additional item Poro-Snax in the Howling Abyss map that could be used, as the name suggests, to feed Poros. When vision trinkets were added, this effect was removed and replaced with all players being given one free Poro-Snax in the trinket slot, regardless of masteries taken.
Your potions, flasks, and elixirs last 10% longer. Additionally, your Health Potions are replaced with Total Biscuits of Rejuvenation that restore an additional 20 health and 10 mana instantly upon consumption.