When you eat a mana cookie, you also eat two diluted pools worth of mana, which is a bit more than the amount you get from feeding a Gourmaryllis a steak and a cooked porkchop (which would also give the player full hunger and full saturation). And you still need to make cookies in the first place.
The Fruit of Grisaia – I mean, it's a relic, for which you had to defeat the gaia guardian one or more times. At that point you've "beaten" Botania and are allowed an infinitely nommable apple. It also costs a bit over two diluted pool's worth of mana to fill your saturation from zero to max with the fruit.
Side note: My preferred vanilla food is cooked porkchop because it also completely bypasses the farming system by requiring only a hoglin farm based on natural spawning. Eat two of those in a row, and you also have full hunger bar and full saturation. (And you didn't even need to make or buy cookies.)