In a medium heatproof bowl set over a pan of simmering water, melt the dark and white chocolates together. Scrape into a smaller bowl and let cool slightly.
Put the crushed cookies on a small plate. Line 2 baking sheets with wax paper and place one in the freezer. Fill a cup with ice water.
Working very quickly, scoop a 1-tablespoon-size scoop of ice cream, packing it tightly. Transfer it to the melted chocolate. Using a skewer, poke the rounded top of the ice cream and coat the ball in the chocolate. Lift the bonbon, allowing the excess chocolate to drip into the bowl. Dip the bottom of the bonbon in the cookie crumbs and set on the baking sheet. Sprinkle salt on top. Let stand for 10 seconds, then transfer the bonbon to the baking sheet in the freezer. Repeat to form the remaining bonbons; dip the ice cream scoop in the ice water between scoops. Freeze the bonbons until firm, 30 minutes, then serve.