The best substitute is fondant. However, I'd recommend using marzipan, as it has more flavor and wouldn't make this dessert as sweet as with fondant. If someone is allergic or sensitive to almond marzipan, you can make your own u003ca href=u0022https://realfood.tesco.com/recipes/nut-free-marzipan.htmlu0022 target=u0022_blanku0022 rel=u0022noreferrer noopeneru0022u003enut-free marzipanu003c/au003e or try a different type of nut, such as u003ca href=u0022https://www.daringgourmet.com/pistachio-marzipan/u0022 target=u0022_blanku0022 rel=u0022noreferrer noopeneru0022u003epistachiosu003c/au003e.