Place the eggs yolks, cornstarch, molasses, salt and ½ cup of the milk in a medium bowl and whisk until smooth.
In a medium, heavy-bottomed pot, place the remaining 1½ cups milk, 1 cup whipping cream, brown sugar and vanilla extract. Set over medium heat, bring to just below a boil, and then remove from the heat.
Very slowly whisk 1/2 cup of the hot milk/cream mixture into the egg yolk mixture to temper it. Now very slowly whisk this mixture into the hot milk/cream mixture remaining in the pot.
Set the pot back over medium heat, bring to simmer, and whisk and cook until the mixture is thick like pudding. Removed from the heat and whisk in the butter until melted and well incorporated.
Carefully pour the mixture into 6 (3/4 cup) decorative glasses or ramekins and cool to room temperature. Now wrap and refrigerate puddings until well chilled and set, at least 4 hours, or overnight. Serve pudding as is, or, if desired, dress each one up with a dollop of whipped cream and a sprinkling of nutmeg.