There should be additional farmable/harvestable ingredients that aren't food in themselves, but can provide specific buffs to already cooked food: herbs and seasonings. The way I imagine it working, any cauldron cooked food can be re-cooked with a seasoning to provide a specific buff to that food, or maybe choose an "auxiliary ingredient" when making the food the first place. A food can only have one buff ingredient applied (choosing a new buff ingredient overrides its existing buff with a new one.)
These seasonings should be more rare to find and more difficult/intensive to grow than regular ingredients.
Here are a few I thought of:
Onion: Increases health of food by a percentage (20-30%?) Found in bulb form, wild, like carrot/turnip seeds, can be re-planted and farmed.
Garlic: Same as onion, but buffs stamina instead of health.
Salt: Same as onion, but buffs the food duration. Mining rocks along shore lines has a (small) random chance of giving a few salt. Leviathans have salt crystal outcrops that grow on them, and provide more salt than random rocks on shore. It can also be found in small quantities in chests. Another option would be to have salt only sold by the trader (since it was a valuable trade commodity in the dark ages.)
Mint: Adds a frost resistance buff to food, but for a much shorter time than mead. Grows in bush form like strawberries/blueberries, can be re-planted and farmed, but has a longer re-growth time than usual crops.
Mustard seed: Same as mint, but with a fire resistance buff.
Sorrel: Same as mint, but with a poison resistance buff.
Thyme: Same as mint, but with spirit resistance.
Hops: Same as mint, but with physical damage resistance.