Hands down my favorite apples to not only eat but cook with are granny smith and honey crisp. Granny smith apples are firm and tart. They are perfect for cooking. Honey crisp, are also firm but they are a lot sweeter than granny smith. They won't cook down too much so they are still great for cooking. If you can't decide between the two, you can also do a combo for a bit of sweetness and a bit of tart. Other apple varieties that are good for cooking are: Jonagolds, Melrose, Winesap and Braeburn.