In a large heavy bottom pan over medium heat combine half & half, sweetened condensed milk and instant coffee crystals. Stir until coffee crystals dissolve.

In a separate bowl, whisk the egg yolk and gradually add 4-5 ladles of hot mixture into the egg yolk while whisking. Return the tempered egg mixture into the the hot milk mixture and stir to combine.

Note: This is called tempering the egg. You're bringing the egg to temperature and incorporating without overcooking and scrambling the egg.

Bring mixture to a high simmer and cook over medium heat for 2 minutes, stirring constantly. Turn heat off.

Add whiskey, rum, chocolate syrup and vanilla extract and stir to combine.

Allow to cool at room temperature. Cover with plastic wrap directly over the liquid and chill in the refrigerator at least 8 hours, best overnight.

Remove the plastic wrap and stir mixture well. Pour chilled mixture through a sieve into another pot or container. This will remove any egg particles or skin that may have formed while cooling.

Transfer to bottles or container with lid. Keep refrigerated. Stores well in the refrigerator up to 2 months. Makes about 4½ cups or 9 4-ounce servings.

Note: I always make a triple batch and fill 4 full 750 ml wine bottles, plus a little extra for the chef. Makes lovely gift for family and friends.