Place the chocolates and Scotch in a medium heat-proof bowl and set aside.
Whisk egg yolks and sugar in a separate heat-proof bowl and set aside.
Heat cream and milk over moderate heat until bubbles form around edges.
Slowly stream about half of the scalded cream mixture into the eggs, whisking continuously. Pour the tempered egg mixture back into saucepan with the remaining cream and whisk to combine.
Continue to cook over moderate heat, stirring continuously with a wooden spoon until it is quite thick (mixture should coat the back of the spoon without running); do not allow eggs to scramble or mixture to boil.
Pour the custard through a sieve placed over the chocolates and allow mixture to sit for 2 – 3 minutes. Whisk mixture, starting in center of bowl, and working your way toward the outside of the bowl. (You can use an immersion/stick blender to make quick work of this part.) Once the mixture has completely combined and is smooth, strain it again through a fine mesh sieve set over a pitcher or other container with a spout.
Pour into 8 demitasse cups or 6 (4-oz) ramekins, set in a larger baking pan. Cover the entire dish with foil carefully so as not to touch the tops of the custards. Refrigerate at least 3 hours until firm.
Allow custards to come to room temperature before serving. Garnish with fresh whipped cream.
*This scotch has a distinctive, mellow flavor that harmonizes beautifully with the milk chocolate. If you substitute another scotch, look for one with a fruity or honey flavor profile rather than one that is peaty or smoky. You may also substitute Chambord or another liqueur.
**Valrhona milk chocolate is carried at Sur la Table and through online resources such as chocosphere.com