Core apples, then score skin around each apple a few times. Cut a small slice from top and bottom to make each apple more stable and to make room for crumble topping.
Finely chop chocolate and combine with hazelnuts.
Arrange apples in a parchment-lined baking dish.
Fill the center of each apple generously with chocolate and hazelnut mixture (reserve about 2 tablespoons for topping).
Preheat oven to 350°F. For crumble, combine oats, coconut, flour, butter, and brown sugar; mix well.
Top each apple generously with crumble mixture, creating a small mound on top of each apple; sprinkle with reserved chocolate and hazelnut mixture.
Bake apples 20–25 minutes or until crumble is golden and apples start to soften. Serve with a drizzle of maple syrup or honey. Makes 8 servings.