Transfer the buttercream into a pastry bag tip with a star tip; I used French star tip #4ft. Pair the macaron shells by size, then pipe a ring of buttercream onto one half, leaving a small space in the center for the cranberry jelly. Place the remaining 1/3 cup jelly into a pastry bag, or use a small spoon, and add a small dollop into the center of each macaron. Sandwich the cookies together and place onto a wire rack. If desired, melt ¼ cup white chocolate chips, transfer into a ziplock bag, then drizzle over the cookies.