Line a medium-size bowl with 2 sheets of aluminum foil. Scoop the vanilla ice cream into balls and place in bowl. Freeze for 30 minutes.
Repeat with the chocolate ice cream, placing it on top of the vanilla and making the top as even as possible. Freeze for at least 2 and up to 24 hours.
Invert bowl onto a serving platter. Remove bowl and foil. Sprinkle with the crushed candy. Use a knife to slice the bombe into wedges, running it under hot water in between cuts. Serve immediately.
In Advance: The Ice Cream Bombe must be made at least a day ahead of time. You can unmold it the morning of the party, inverting it onto a serving platter, and return it to the freezer. Sprinkle the crushed candies over the top just before serving.