Wash and thoroughly dry your apples. Remove the stems and insert wooden sticks or popsicle sticks about halfway into each apple through the stem end.
Line a baking sheet with parchment paper and lightly coat with cooking spray. Refrigerate the apples for 30 minutes before dipping to help the caramel set faster.
In a medium-sized, heavy-bottomed saucepan, combine the sugar, water, and corn syrup. Place over medium-high heat and stir until the sugar dissolves.
Once dissolved, stop stirring and allow the mixture to boil until it turns a deep amber color, about 8-10 minutes. The temperature should reach approximately 340°F (170°C) on a candy thermometer.
When your caramel reaches the perfect amber color, carefully add the room temperature cream (it will bubble vigorously—stand back!). Whisk continuously until smooth.
Reduce heat to low and add butter and miso paste, whisking until fully incorporated and silky smooth. The miso should be completely dissolved with no lumps.
Remove from heat and stir in vanilla extract and sea salt.
Allow the caramel to cool slightly until it thickens a bit—about 5 minutes. Test the consistency by dipping a spoon; the caramel should coat the back of it evenly.
Tilt the saucepan slightly and carefully dip each apple, rotating to coat evenly. Let excess caramel drip back into the pan for a few seconds. For a more professional finish, scrape the bottom of the apple against the side of the pan to remove excess caramel.
If using toppings, roll the freshly dipped apples in your chosen ingredients immediately, before the caramel sets.
Place the decorated apples on the prepared baking sheet. Refrigerate for at least 45 minutes to set completely.