Heat butter, brown sugar, corn syrup, and sweetened condensed milk in a heavy saucepan over Medium-High heat.
Bring to a boil, stirring occasionally. Continue cooking and stirring until a candy thermometer reaches 248 degrees, about 30 minutes.
Remove from heat, and stir in vanilla.
Place a stick into each apple and dip into caramel, turning to completely coat.
Allow excess to drip off, using a spoon if necessary, then place on parchment paper to set, about 2 to 3 hours.
Place chocolate in a large bowl and heat in the microwave for 1 minute on HIGH. Stir, then continue cooking and stirring in 15 second intervals until chocolate is melted and smooth.
Dip caramel covered apples in the melted chocolate, using a large spoon to cover all sides, or simply drizzle over the top.
Place on parchment paper to set. Sprinkle with toppings as chocolate begins to harden, but is still sticky.
You may have more caramel than you need, so grab some pretzel rods or candy molds and additional chocolate for the leftovers.Chocolate will begin to spot/turn grey over time if chocolate is not tempered correctly. It will not affect the taste, just the appearance.