In a medium saucepan, over medium heat combine the brown sugar, butter and corn syrup. Once they are melted, add the can of sweetened condensed milk and stir. Heat until it comes to 245 degrees F. Stir continuously with a wooden spoon. Be careful not to burn. Remove from heat and add the vanilla. Let cool slightly before dipping apples.
Place caramel dipped apples on half sheet pans lined with parchment paper. Let the caramel harden in a cool place. Then dip in melted chocolate. While the chocolate is still wet, roll the apples in your desired toppings.
If you are doing a topping such as candy pieces (such as M&M's), let the chocolate harden slightly before pressing on the candy. Otherwise it will slide off.
Let the apples dry in a cool location.
Video
Notes
Storing Caramel Apples:If it's winter, I often times will store them in our garage on a folding table. Once the chocolate is set package up the caramel apples in food safe bags and tie up with a twist tie.