Spread the whole hazelnuts and coconut on a baking sheet and toast until deep golden, 8 to 10 minutes.
Let cool, then transfer to a food processor.
Add the cereal and condensed milk and pulse until the mixture is finely ground.
Lightly spray 6 muffin-tin cups with cooking spray. Divide the coconut mixture among the cups. Wet your fingers, then press the coconut mixture into the bottom and up the side of each cup. Freeze until firm, at least 20 minutes.
Remove the muffin pan from the freezer. Fill the crusts with coconut ice cream, smoothing the tops. Freeze until firm, about 40 minutes.
Top each ice cream cupcake with a scoop of chocolate ice cream (make the scoop flat on the bottom so it sits on top of the coconut ice cream).
Serve immediately or cover and freeze for up to 2 days. To unmold, run an offset spatula around the edge of each cup, then pry out the cupcakes. Top with chopped hazelnuts.
