Whisk egg yolks with stand mixer, until light in color, about 2 minutes. Gradually add ⅓ cup sugar and continue to beat until it is completely dissolved. Set aside.
In medium saucepan, combine milk, heavy cream and all spices plus minced Cuban oregano and just bring to boil, stirring occasionally. Remove from heat and strain.
Gradually temper hot cream mixture into egg and sugar mixture., and then return everything to saucepan and cook until the mixture reaches 160 degrees. Remove from heat, stir in brandy and black currants and pour mixture into medium mixing bowl. Place in refrigerator to chill for 2 hours.
Using stand mixer, whip egg whites to soft peaks. With mixer running, gradually add 1 tablespoon of sugar and beat until stiff peaks form. Gently whisk egg whites into chilled cream mixture.
Return eggnog to refrigerator, and chill for at least 4 hours.
Ladle eggnog into martini glasses and garnish with 1 leaf of Cuban oregano and 3 black currants