Special equipment: Six 6-ounce ramekins; a roasting pan; a kitchen torch
Preheat the oven to 325 degrees F. Whisk together the egg yolks and 3/4 cup of the sugar in a medium bowl until pale yellow and thick.
Put the cream in a medium saucepan. Using a paring knife, split the vanilla bean lengthwise down the middle, scrape out the seeds and add them to saucepan along with the rum or brandy, if using, and the nutmeg. Bring the cream to a simmer over low heat, stirring constantly with a rubber spatula. (Do not let the mixture boil or it may overflow.)
Remove the cream mixture from the heat and temper the yolks by gradually whisking the hot cream into the yolk mixture. Do not add the hot cream too quickly or the eggs will scramble.
Using a ladle, carefully divide the custard among the six 6-ounce ramekins, filling each about 3/4 full. Put the ramekins in a roasting pan and carefully fill the pan with enough warm water to come halfway up the sides of the ramekins.
Bake the custards until barely set around the edges but still slightly jiggly in the center when the ramekins are shaken gently, about 40 minutes. Keep an eye on the custards toward the end to make sure they don¿t brown. If they start to brown, cover the pan loosely with foil.
Transfer the custards to a cooling rack and cool to room temperature. Refrigerate the custards for at least 3 hours or preferably overnight.
Sprinkle about 1 tablespoon of sugar over the top of each custard. Using a kitchen torch held about 2 inches above the surface, heat the sugar until it browns and forms a a crust. Alternately, put the custards under the broiler to caramelize the sugar. Serve at once.
[warning] Propane gas torches are highly flammable and should be kept away from heat, open flame, and prolonged exposure to sunlight. They should only be used in well-ventilated areas. When lighting a propane gas torch, place the torch on a flat, steady surface, facing away from you. Light the match or lighter and then open the gas valve. Light the gas jet, and blow out the match. Always turn off the burner valve to "finger tight" when finished using the torch. Children should never use a propane gas torch without adult supervision.