Step 1

Pour cream or milk into the top of a double boiler.

Step 2

In a separate small bowl, whisk the sugar and flour together and when the water begins to boil, whisk the sugar and flour mixture into the milk.

Step 3

Separate the eggs, reserving the egg whites in the refrigerator for another use, or to add to eggnog, if desired.

Step 4

In that same bowl you used for the sugar, beat the egg yolks until lemon colored and thickened.

Step 5

Temper the eggs with a few scoops of the hot milk, adding the milk to the eggs a little at a time, and whisking constantly while adding. Transfer the tempered egg mixture into the hot milk, whisking constantly until fully incorporated.

Step 6

Cook, stirring constantly, until mixture reaches 180 degrees on a candy thermometer, about 10 minutes. You'll know that the custard is ready when it coats the back of a spoon and you can drag your finger through the middle, leaving a path.

Step 7

Remove from heat and strain through a cheesecloth covered sieve; set aside to cool. Once cooled, stir in your choice of extract flavoring; add nutmeg to taste (I do about 12 passes on a microplane), taste and add additional extract or nutmeg, as desired. Cover and refrigerate until cold.

Step 8

If desired, just before serving, whip the egg whites separately with a pinch of cream of tartar, until fluffy. Whisk into the cooled custard before pouring into individual mugs. This step can be omitted if desired.

Step 9

Boiled custard can be used as a beverage, with or without a splash of bourbon or rum, and is also excellent over fresh or canned fruit, or when used as a dessert sauce over cake. Should keep about a week in the fridge.