Line an 8x8-inch pan with parchment, leaving an overhang on two sides.

Combine the chocolate chips and two-thirds of the condensed milk in a saucepan over low heat, stirring constantly until melted and smooth, about 3 minutes.

Stir in 1/2 teaspoon vanilla, then pour into the pan and spread into an even layer.

In a separate saucepan, melt the white chocolate chips with the remaining condensed milk over low heat, stirring until smooth, about 3 minutes.

Stir in the raspberry jam and remaining vanilla until streaked but not fully blended; a few drops of food coloring deepen the pink if you like.

Pour the raspberry layer over the chocolate layer and swirl gently with a knife tip for a marbled look.

Refrigerate uncovered for 2 hours, until the fudge is firm enough that pressing the center leaves no indent.

Lift the fudge out using the parchment overhang, cut into 1.5-inch pieces, then trim the corners off each piece to round it into an oval football shape.

Pipe thin white icing laces across the center of each piece if you want the full look, or leave them plain for a simpler serve.