Harnquist seems to have several different requests to satisfy his hunger, but I don't know what all they are. It seems to depend on the skill of the individual.
I think all the cooking quests have the player make something as part of the quest. I don't know if you could just give the completed item and bypass all the intermediate steps.
As for harvesting, various quests require apples, lake mushrooms, night mushrooms, carrots, barberry root, juiceberries, wragberries, lavender, devil's claw, kingsfoil leaf, wyn reed, red mangrove, sicklepod, hops, white oak bark, blackbush stem, carp, trout.