4 small peppermint or sugar-free peppermint hard candies, crushed
Coarsely ground coffee beans (optional)
Line a 1-quart bowl with plastic wrap. Freeze 30 minutes.
For filling, in a bowl stir together softened ice cream and peppermint extract just until combined. Spoon into prepared bowl, packing firmly. Cover and freeze 4 hours or until firm.
In bowl, stir together graham cracker crumbs and melted butter until evenly coated. Sprinkle over ice cream; press to pack very firmly. Cover and freeze 24 hours or until firm.
In a bowl, dissolve espresso powder in water. Gently fold espresso into whipped topping until just combined (be careful not to over mix; there may be some streaks left). Cover and chill until ready to serve.
Unmold bombe onto a serving platter, loosening with a thin spatula, if necessary. Remove and discard plastic wrap.
Spoon espresso mixture into a pastry bag fitted with a star tip. Quickly pipe espresso mixture over the bombe to enclose. Sprinkle with crushed peppermints and, if desired, ground coffee beans. Return to freezer at least 1 hour before serving.