Step 1: Thoroughly wash the apples in hot water to remove any wax, dry them completely, and remove the stems. Insert a wooden stick into the center of each apple through the stem end.
Step 2: Line a baking sheet with parchment paper and lightly grease it with butter or non-stick spray to prevent the cauldron caramel apples from sticking.
Step 3: In a medium, heavy-bottomed saucepan, combine the sugar, corn syrup, and butter. Stir over medium heat until the butter is melted and the sugar is dissolved.
Step 4: Attach a candy thermometer to the side of the pan. Bring the mixture to a boil without stirring. Continue cooking until the thermometer reaches 245°F (118°C).
Step 5: Remove the pan from the heat and slowly whisk in the heavy cream, vanilla, salt, and black gel food coloring. Be careful, as the mixture will bubble up significantly.
Step 6: Let the caramel sit for 2-3 minutes until most of the bubbles have disappeared and it has thickened slightly.
Step 7: Dip each apple into the dark caramel, tilting the pan to ensure a full coat. Lift the apple and swirl it gently to allow the excess to drip back into the pan.
Step 8: Place the finished cauldron caramel apples onto the prepared parchment paper. Allow them to cool and set completely at room temperature for at least 1 hour before serving.