Cut Pop-Tart in half down the short side. Using a ring mold or knife, cut each half into semicircles.

Place the semicircles frosting side down. Pipe frosting onto the exposed pastry sides, leaving about ¼ inch at the border

Line the edges of one semicircle with mini marshmallows.

TRICK: In that same semicircle, make a tiny well in the center of the frosting. Add a drop of corn syrup and 3 drops of blue food gel to a few sandwiches, guests will only know which is which upon first bite

Cover with the other semicircle, lining up the curved sides and creating a sandwich.