Ingredients

• 3/4 cup walnuts (2 1/2 ounces), toasted, cooled, and chopped
• 3/4 cup lightly crushed chocolate wafer cookies
• 3 pints cherry or cherry vanilla ice cream, softened slightly
• 1 pint chocolate ice cream, softened slightly
• 6 ounces bittersweet chocolate (no more than 60% cacao), finely chopped
• 1/2 stick unsalted butter, cut into pieces
• 1/4 cup vegetable oil
• 1 maraschino cherry with stem
• a 2- to 2 1/2-quart bowl (about 8 inches in diameter)

Instructions

1. Line bowl with plastic wrap, leaving an overhang all around.
2. Stir walnuts and chocolate cookies into cherry ice cream in another bowl. Transfer ice cream to lined bowl and spread evenly over bottom and up sides, leaving a crater in center. Freeze until firm, about 45 minutes.
3. Scoop chocolate ice cream into crater in cherry ice cream, then smooth top with an offset spatula. Freeze until firm, about 1 hour.
4. Meanwhile, melt chocolate with butter and oil in a heatproof medium bowl set over a pot of simmering water, stirring. Remove from heat and cool slightly.
5. Invert bombe onto a rack set over a baking sheet and remove plastic wrap. Make a small indentation in top and place maraschino cherry into ice cream so that the cherry is submerged but stem sticks straight up (like a fuse).
6. Ladle chocolate sauce on top of bombe (avoiding cherry stem), letting it drip over sides to coat thoroughly. Freeze until chocolate coating is set, about 30 minutes.
7. To serve, cut into wedges.