To make these Triple Chocolate Cupcakes gluten free, replace the all-purpose flour with a reliable 1:1 gluten-free baking flour blend that includes xanthan gum or a similar binder. Also confirm that the cocoa powder, confectioners’ sugar, bittersweet chocolate, vanilla extract, baking powder, corn syrup, cream cheese, and sour cream are labeled gluten free, since brands and manufacturing practices can vary. Because gluten-free cupcake batter can sometimes be slightly more delicate, avoid overmixing and allow the cupcakes to cool fully before filling and frosting. For anyone with celiac disease or severe gluten sensitivity, use clean bowls, mixers, liners, spatulas, decorating bags, and pans to avoid cross-contact.