Preheat the oven to 300°F (150°C).
In a saucepan, combine the heavy cream, sugar, and instant coffee. Heat over medium until just simmering.
In a separate bowl, whisk together the egg yolks, Irish whiskey, and vanilla extract until combined.
Slowly pour the hot cream mixture into the egg mixture, whisking continuously.
Strain the mixture through a fine-mesh sieve into a measuring cup or bowl.
Divide the custard mixture among ramekins and place them in a baking dish. Fill the dish with hot water halfway up the sides of the ramekins.
Bake the custards for 30-35 minutes, or until set but still jiggly in the center.
Remove the ramekins from the water bath and let them cool at room temperature before refrigerating for at least 2 hours.
When ready to serve, sprinkle a thin layer of sugar over each custard and use a kitchen torch to caramelize the top.
Let the caramelized sugar cool for a few minutes before serving to allow it to harden.