In a blender or food processor, whirl gingersnaps and brown sugar to fine crumbs.
With a small, sharp knife, starting from stem ends, cut around cores to about 3/4 of the way through apples; scoop out cores with a spoon, making a 1 1/2-inch-wide cavity and leaving bases intact. Set apples slightly apart in a shallow 2- to 3-quart baking dish.
Spoon 1 tablespoon gingersnap mixture into each cavity and top with 1/2 tablespoon butter. Sprinkle apples evenly with remaining gingersnap mixture.
Bake in a 375º regular or convection oven until apples are tender when pierced, about 45 minutes. Transfer to individual bowls and pour 2 tablespoons cream around each if desired.