Heat the heavy cream over medium heat, whisking to dissolve the espresso powder. Remove from heat and allow to cool to room temperature.

In a bowl combine the egg yolks and sugar. Stir for a couple minutes until the mixture turns from bright yellow to a paler yellow. Slowly whisk in the heavy cream-espresso mixture and the vanilla extract. Pour the batter into your ramekins.

Place the ramekins in a large casserole dish or a baking sheet with a tall lip. Fill the baking dish with water so the ramekins are half submerged in the water. Bake at 325°F for 45-48 minutes. The custard should look set but have a slight jiggle in the center (like a solid custard). If it seems too liquidy, allow them to cook for a few more minutes. Ramekin size can really make a difference here, so use your best judgement. Take care when removing the baking dish from the oven as the water will be very hot. You do not want to splash it on your skin.

Allow the custards to cool. Then cover and refrigerate for at least two hours or overnight. Before serving, sprinkle a thin layer of sugar over the top and caramelize with a kitchen torch or under the broiler.