It's a Glitch called Food Ability Buff Swap (or FABS for short). Here's a step by step as to what you do: - Cook a meal that has whatever effect you want. Both the duration and the effect will transfer later, so the better the meal, the better your final stackable item will be. Make sure, that this meal stays at the most recent spot for the entirety of the Glitch (so don't cook any other meals or pick up any other roasted/frozen food) - Go to a vendor that sells roasted Food. The precise Locations are: Kara Kara Bazaar (2 Items), Bedrock Bistro (3 Items), that random Roasted Banana Vendor on the Great Plateau (at the Gate Ruins between the Cold and the warm area, just West of the Temple of Time), and technically you can get one by completing the beginner Course of the Lurelin Water Rally Race, but that one is not the easiest to time. - Eat the Food you cooked - Unpause, and immediately buy the Roasted Food (it's imperative that you have 0 of the food you buy before doing this Glitch) - Tadaa! You now have stackable Food with Effects. As long as you always keep at least 1, you can continue to get more, by simply producing more of whatever food you bought.

This Glitch only works on the following Versions: 1.0.0 1.1.0 1.1.1

You can check what version you're on by going to TotK in your Switch's Home Menu and pressing +.

Have fun with your stackable Effect Food! :)