In a medium mixing bowl, combine the white chocolate chips, butter, vanilla extract, and sweetened condensed milk. Microwave the mixture in 30-second intervals, stirring thoroughly after each session to ensure even melting. Shift to 15-second bursts as needed, stirring diligently between each heating, until the chocolate becomes fully melted and silky smooth. Withdraw the bowl from the microwave and immediately incorporate the chopped pecans, mixing well to evenly distribute. Prepare a baking dish by lining it neatly with parchment paper. Transfer the melted fudge mixture into the lined dish, smoothing it out to an even thickness of about one inch or as desired. Generously drizzle the room-temperature caramel sauce over the top of the fudge. Using a knife, gently swirl through the caramel and chocolate to create an elegant marbled effect. Place the baking dish in the refrigerator and allow the fudge to chill thoroughly until fully set. Once firm, slice into one-inch squares and serve.