Wash and thoroughly dry the apples. Remove any stems and insert wooden sticks into the top center of each apple. Set them on a parchment paper-lined baking sheet, and make sure they are at room temperature.
In a heavy-bottomed saucepan over medium heat, melt the butter.Stir in the brown sugar, corn syrup, and a pinch of salt. Continue stirring until the mixture comes to a boil.
Once the mixture is boiling, reduce the heat to medium-low and slowly pour in the sweetened condensed milk while stirring constantly.
Continue to cook and stir the caramel mixture until it reaches the soft ball stage on a candy thermometer. This temperature is typically around 235°F to 240°F (113°C to 116°C). It should take about 10-15 minutes. The soft ball stage is when a small amount of the caramel dropped into cold water forms a soft, pliable ball.
Remove the caramel from the heat and stir in the vanilla extract. Be cautious, as the mixture will bubble up when you add the vanilla.
Quickly dip each apple into the hot caramel, swirling and rotating to coat the apple evenly. Allow any excess caramel to drip back into the saucepan.
Place the caramel-coated apples back onto the parchment-lined baking sheet. Allow them to cool and set at room temperature for about 1-2 hours. You can also place them in the refrigerator to speed up the setting process.
If you want to add extra flavor and texture, consider rolling the caramel apples in chopped nuts, mini chocolate chips, crushed cookies, or drizzling them with melted chocolate once the caramel has partially set.
Once the caramel has fully set, your homemade caramel apples are ready to enjoy! They can be wrapped in cellophane or wax paper for gifting or simply enjoyed as a delightful fall treat.