Crispy meringues with a soft, gooey, marshmallow-like center sandwiched together with a white chocolate ganache and raspberry filling. These meringue sandwiches will satisfy your sweet tooth. The fairly short baking and cooling time helps creates the gooey marshmallow-like center. Superfine sugar dissolves easier into the egg whites than regular granulated sugar, and also helps to maintain a light textured meringue. Make your own superfine sugar by putting granulated sugar into a food processor, blender, or small food grinder and processing into fine granules. Vinegar is an acid used to help stabilize and give more volume to the beaten egg whites.