Preparation: Preheat oven to 300°F (150°C). Arrange 4 ramekins in a baking dish and boil water for the water bath.

Cream Mixture: Heat heavy cream, ¼ cup sugar, and salt in a saucepan over medium heat until sugar dissolves, stirring occasionally.

Temper Yolks: Whisk egg yolks in a bowl. Gradually whisk in warm cream mixture to avoid curdling the yolks.

Coffee Infusion: Mix espresso powder and Kahlua, then stir into custard mixture. Strain through a fine mesh sieve into a bowl or measuring cup with a spout.

Bake Custard: Evenly divide the mixture into ramekins. Fill baking dish halfway with boiling water. Bake 25–35 minutes (40–45 minutes for deeper ramekins), until custards have a slight jiggle in the center.

Cooling: Cool ramekins on a wire rack for about 4 hours, then refrigerate, covered, at least 2 hours or overnight.

Caramelize: Sprinkle 1 tablespoon sugar over each chilled custard. Caramelize using a kitchen torch until golden. Alternatively, broil custards briefly under a preheated broiler until the sugar melts and browns.