In a medium saucepan, combine brown sugar, heavy cream, butter, and salt over medium heat. Stir continuously for 4-5 minutes until thickened and deep caramel color is reached. Remove from heat and mix in vanilla extract.

In a heatproof bowl, melt the white chocolate chips using a double boiler or microwave, heating in short bursts, until smooth and glossy.

Slowly pour the caramel into the melted white chocolate, stirring continuously. Add sweetened condensed milk and mix until shiny and uniform.

Gently fold in toasted pecans, ensuring even distribution without overmixing.

Line an 8x8-inch baking pan with parchment paper. Pour and spread fudge mixture evenly. Optional: swirl in extra caramel or sprinkle pecans. Chill for 3-4 hours until firm.

Lift fudge out using parchment overhang, slice into squares for serving. Store leftovers in an airtight container in the fridge.