In a medium saucepan melt better, add 2 tablespoons of the brown sugar and stir until smooth. Add chopped apples and cook on medium-low heat until softened, about 5-7 minutes. Transfer to a bowl and set aside.

In same saucepan add apple cider, vinegar, remaining brown and cinnamon and bring to a boil. Reduce heat and simmer for approximately 30 to 40 minutes, stirring often, until liquid is thickened and measures about 3/4 cup.

While apple cider is reducing, in a large mixing bowl whip cream cheese and sugar, add egg yolk and vanilla and beat until well combined.

Add 1/4 cup of reduced cider to apple mixture.

Preheat oven to 375 degrees. Arrange tart shells on cookie sheets. Spoon cream cheese into each tart shell, filling almost to the top, divide the cooked apple mixture evenly over all the tart shells. Bake for 18-20 minutes, until shells are golden.

Remove from oven and cool. Drizzle remaining apple cider reduction over the top of the cooled tartlets.

Refrigerate or freeze any unserved tartlets.