Food healing during a short or long rest I could understand (maybe making 'eating food' the mechanic behind expending a hit-dice to heal), but having food do an instant heal and setting no limit on how many times it can be used completely devalues healing potions, spells etc and flies in the face of normal D&D rules. Healing up isn't supposed to be easy, you aren't supposed to be able to start each fight at full HP, fully rested and with all spells prepared.
You mostly cannot, especially the spell part. Except in the beginning.
