Spray a 8 or 9-inch square pan with baking spray and line with parchment paper.
In a large microwave safe bowl, combine dark chocolate chips and sweetened condensed milk
Heat on high heat in 30 second intervals, stirring in between, until nice and smooth.
Stir in raspberry jam, vanilla extract, and salt until combined.
Remove 1/3 cup white chocolate chips form the pacakge and set aside.
Add remaining white chocolate chips to the mixture and stir. The dark chocolate mixture will be still be warm at this point so the chips will melt partially and create a marbling effect - depending on how hot it is.
Spoon the fudge mixture into the prepared pan and refrigerate until firm.