The coffee, which is best made using medium-roast beans, can be made ahead and added to the slow cooker two hours before you plan to serve dessert.

1. Add the chilled coffee to the slow cooker. Cover and cook on low for 1 hour. If you're using fresh-brewed coffee, you can skip this step.

2. Stir in the sugar until it's dissolved; cover and cook on low for 1 hour.

3. To serve, ladle into heatproof mugs. Add whiskey to taste and garnish with a dollop of whipped cream.