Prep: 7 minutes. If you don't want to use the liqueur, just leave it out. You'll still get a rich chocolate-coffee flavor from the syrup and the ice cream.
Combine chocolate syrup and liqueur in a small bowl, stirring well with a whisk. Place 1/4 cup chocolate or vanilla ice cream into each of 4 glasses. Drizzle with 1 1/2 teaspoons chocolate syrup mixture and about 2 tablespoons crumbled cookies. Spoon 1/4 cup coffee ice cream over crumbs in each dish, and top with remaining syrup and cookies.
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