In a medium, microwave-safe bowl with high sides (to prevent splattering), combine the butter, sweetened condensed milk, and brown sugar. Heat in the microwave for about 3 minutes, pausing every minute to stir. By the end of this time, the butter should be fully melted, and the sugar should be dissolved.

Stir the caramel mixture thoroughly, then microwave for an additional 2 minutes, stirring every 30 seconds. Be cautious, as the caramel will become very hot and may bubble over if left unattended. Use oven mitts to safely handle the bowl while removing it from the microwave. The caramel should be thick and golden in color. To ensure proper setting, it needs to reach the “soft ball stage” (112°C / 234°F). You can verify this with a candy thermometer. Avoid overheating, as this will make the caramel set too hard.

Once the caramel reaches the right stage, add the white chocolate pieces and sea salt. Stir well until the chocolate melts completely and the mixture is smooth. Cover the bowl with plastic wrap and refrigerate for at least 3-4 hours, allowing the caramel to firm up.

In a medium saucepan, combine the butter, sweetened condensed milk, and brown sugar. Cook over low heat, stirring frequently, until the butter melts and the sugar dissolves completely.

Increase the heat to medium and continue stirring as the mixture begins to simmer and thicken. This process can take about 5-6 minutes. The caramel should be thick and golden in color, reaching the “soft ball stage” (112°C / 234°F). Use a candy thermometer to check the temperature.

Once the caramel is ready, remove it from the heat and immediately stir in the white chocolate and sea salt. Mix until the chocolate is fully melted and the mixture is smooth. Transfer the caramel fudge to a medium-sized bowl, cover it with plastic wrap, and refrigerate for at least 3-4 hours to set.

Let the caramel fudge sit at room temperature for 5-10 minutes to soften slightly. Line a large baking tray with baking or parchment paper.

Melt the chocolate in a microwave-safe bowl by heating it in 30-second intervals, stirring after each interval, until it is smooth and fully melted.

Scoop out tablespoons of the caramel fudge and roll them into balls with your hands. Dip each ball into the melted chocolate, using a fork to lift it out and place it onto the prepared baking tray.

Repeat with the remaining fudge truffles. If desired, sprinkle crushed nuts on top of each truffle.

Refrigerate the truffles for at least 30 minutes to allow the chocolate coating to set. Store any leftovers in an airtight container in the refrigerator.