The Northern Spy is one of my top three apples for baking pies. I like the Northern Spy so much that Lorna and I will make pilgrimages to specific destinations where we know we can get a bag for November pies.
I always use three apples when I bake a pie. In November, two of them must be Northern Spy and Golden Russet, and I like Baldwin for the third but even the Foodie Pilgrim can't always find the Baldwins.
The Northern Spy has a slightly spicy flavor, good acidity, and the slices hold their shape well when baked. I hate it when the inside of a pie is a settled, solid mass of apple-mush!
The Northern Spy has about the same size and coloring as the popular Cortland, so how do you tell them apart? The Spy is speckled and the Cortland is streaked. It's always good to spot a Spy!