Meanwhile, prepare the white chocolate filling. Place the softened butter into a medium-sized bowl and beat with mixer for a few minutes until the butter is light and fluffy. Add in the melted white chocolate. If the melted chocolate softens the butter too much, place the mixture into the refrigerator for 15 minutes, then mix again.
Add the confectioner’s sugar, vanilla and salt. Mix on low speed until the sugar is incorporated, then mix on high speed for 2 to 3 minutes until a fluffy buttercream forms. Add the 2 tablespoons of cranberry jelly last and mix for about 30 seconds, just until it’s incorporated.
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.
Place the macarons into an airtight container and into the refrigerator for at least 1 day to allow the cookies to ‘mature’. This will allow the shells to absorb moisture, softening and becoming more delicious! Take the macarons out of the refrigerator about 30 minutes before enjoying.