Coffee and Frangelico, a hazelnut liqueur, are frozen and then topped with a billowing peak of maple syrup-flavored cream.
Stir 4 cups strongly brewed chilled coffee and 1 cup Frangelico in a medium bowl. Transfer to freezer until slushy but slightly frozen, about 5 hours, stirring twice.
Whisk heavy cream in a medium bowl until soft peaks form. Add pure maple syrup; whisk until soft peaks return.
Divide coffee mixture among 4 large glasses; top with whipped cream, dividing evenly.