Preheat your oven to 300°F (150°C) and prepare a water bath with a 9x9 baking pan filled with hot water.

In a medium saucepan over medium heat, combine heavy cream, 1/4 cup granulated sugar, and kosher salt. Stir until sugar dissolves and cream is warm but not boiling.

In a large mixing bowl, whisk the egg yolks until they lighten in color and become slightly frothy.

Gradually pour the warm cream mixture into the bowl with egg yolks while continuously stirring.

In a small bowl, mix instant espresso powder with Kahlua until fully dissolved and add to the custard mixture. Strain through a fine sieve into a clean bowl.

Distribute the custard mixture into individual ramekins, filling each about 3/4 full. Place ramekins in the baking pan and pour hot water until it reaches halfway up the sides.

Bake for 25-35 minutes until the edges are set but the centers jiggle slightly.

Remove ramekins from water bath and cool at room temperature for 30 minutes. Cover and refrigerate for at least 4 hours or overnight.

Before serving, sprinkle a thin layer of granulated sugar on top of each custard and caramelize using a kitchen torch.