I'm really glad you enjoyed it!
Hope you don't mind my asking, but what do you mean run out of potions? Your potions should be automatically replenished once you've played every ingredient in your supply. You can actually what ingredients you still need to play to reset by clicking on the satchel next to your active items.
The cowbell is definitely kinda' crazy tho, I won't lie - probably warrants a nerf. You can actually find them yourself too though!
It's a problem with the cow potion specifically. As long as the cow potions regenerate themselves, the deck won't reset. The cow potions add a new potion whenever they combine (including higher level ones), so each potion is effectively worth 5 or 6. It's not realistically possible to avoid combining them long enough for the deck to reset, and of course once one pair combine it chains through a bunch of them.
I'm not really sure how to change it without losing the interesting part of needing to avoid combining them. Maybe put a limit of 3 in the deck at any time, or add a rule that maxing out their combination (to where the bottle breaks) removes all remaining ones from the cauldron and the deck.
EDIT: I didn't realize this until I was playing with slimes so I could actually play around the bovine elixir - even if you don't combine them it looks like they keep getting shuffled back in the deck. The bovine potions should definitely get removed from your deck once you play them and only get added back in when combined.
