Preparation of Baking Pan: Begin by lining a 9x9 inch baking pan with parchment paper. Ensure the parchment paper is evenly spread and covers all sides of the pan. Following this, apply a generous layer of butter over the parchment paper. This procedure is crucial for the easy release of caramels once they are set.
Butter and Sugar Mixture: In a large, heavy-bottomed saucepan, commence by melting the unsalted butter over a medium-low heat setting. Once the butter has melted, incorporate the firmly packed dark brown sugar. It is essential to continue stirring until the sugar is thoroughly mixed with the melted butter. Subsequently, blend in the light corn syrup into the mixture. Continue to heat and stir the mixture for approximately three minutes, ensuring the sugar is completely dissolved and the ingredients are well combined.
Incorporation of Sweetened Condensed Milk: Following the previous steps, introduce the sweetened condensed milk into the saucepan. Increase the heat to a medium setting and continue to stir the mixture vigorously. It is imperative to maintain constant stirring to prevent the mixture from sticking to the bottom of the pan and burning. The target temperature for this mixture, as indicated by a candy thermometer, is between 238° and 240° Fahrenheit. Achieving this temperature typically requires a cooking duration of 20 to 30 minutes.
Addition of Vanilla Extract: Upon reaching the desired temperature, remove the saucepan from the heat source. At this juncture, stir in the pure vanilla extract. Ensure that the vanilla extract is thoroughly blended into the mixture.
Cooling Process: Pour the caramel mixture into the previously prepared baking pan. Spread the mixture evenly within the pan and allow it to cool at room temperature. The cooling process is critical and should last approximately 3 to 4 hours, or until the caramel is completely set. During this period, do not cover the caramel mixture.
Cutting and Wrapping: After the caramel has set, use the edges of the parchment paper to lift the caramel out of the baking pan. Employing a sharp knife, cut the caramel into desired sizes. Finally, wrap each individual caramel piece in waxed paper for preservation and presentation.