Preheat over to 325. Arrange six 3/4 cup ramekins in 13x9x2 metal baking pan.
Combine cream, sugar and espresso powder in heavy saucepan. Bring to simmer over medium heat, stirring until sugar dissolves. Remove from heat.
Whisk yolks, cinnamon and nutmeg in medium bowl. Gradually whisk in cream mixture, then vanilla. Divide custard among ramekins.
Pour hot water into pan to come halfway up sides of ramekins. Bake until custards are softly set about 30 minutes. Remove from water. Chill until cold, at least 3 hours.
Preheat boiler. Press 1/2 tablespoon brown sugar through sieve onto each custard. Broil until sugar bubbles and caramelizes about 2 minutes. Chill until topping hardens at least 1 hour and up to 4 hours. Serves cold.