Uncooked apple pies can be made with two apples (or pears), a flour, and either three syrup or one honey or one bucket of milk. Uncooked blueberry pies can be made with six blueberries, two flour, and one honey. Meat pies require two raw meat, an onion, and a flour. They must be baked to be edible.
Onions can be gathered from tall grass, and grown like any other crop. There are no onion seeds -- just plant an onion.
Spoiler
The source is available on github.
Code: LGPL2, Textures: CC by SA and CC0
Mod dependencies: default, farming, vessels, bonemeal?, mobs?, big_trees?
Download: https://github.com/duane-r/dpies/archive/master.zip