Line baking sheet with parchment paper. Set aside.
Wash each apple well, scrubbing off any wax that may be on the apples.
Insert skewer an inch or two in the bottom of the apple
Stir butter, brown sugar, corn syrup and sweetened condensed milk together in a 3 quart saucepan over medium high heat. Attach candy thermometer to the inside of the pan.
Bring to a boil, stirring constantly, and reduce heat to medium.
Cook until candy thermometer reads 248 degrees F (120 degrees C), 25-30 minutes.
Stir constantly to prevent burning. Very important!
Remove caramel from heat and stir in vanilla extract.
Moving quickly, dip each apple into the hot caramel, completely coating the apple. Place on parchment lined baking sheet to cool. Repeat with remaining apples.
Let cool completely before eating.
Can be stored in an air tight container, in the refrigerator, for up to 4 days.