Prepare the apples by inserting sticks into the stems and setting them on a parchment-lined tray for easy handling.
Combine the sugar, butter, and heavy cream in a medium-sized saucepan over medium heat. Stir constantly until the mixture begins to bubble and turn a golden amber color, around 8-10 minutes. Use a candy thermometer to monitor temperature.
Once the caramel reaches 300°F (hard crack stage), remove from heat and stir in the vanilla extract and black food coloring, mixing quickly until evenly combined. Be careful—the mixture will bubble vigorously.
Quickly dip each apple into the toffee, tilting the pan to cover as much surface as possible. Allow excess to drip off before placing the coated apple onto the prepared tray. Repeat with all apples, then let the toffee harden at room temperature for about 15 minutes.
Prepare the chocolate drizzle by melting dark chocolate or black candy melts until smooth and glossy, either in a microwave-safe bowl in 20-second intervals or using a double boiler.
Transfer the melted chocolate into a piping bag or squeeze bottle, then carefully drizzle over the coated apples in a zigzag pattern to add an ominous, spooky effect.
Allow the decorated apples to set for another 10-15 minutes until the drizzle firms up, resulting in a glossy, eerie, black toffee coating with decorative accents.
