To make this recipe gluten free, use a certified gluten-free puff pastry and replace the flour in the custard with a gluten-free flour blend or cornstarch. Also confirm that the vanilla, confectioners’ sugar, and any packaged ingredients are labeled gluten free or free from cross-contact concerns. Because gluten-free puff pastry can be more delicate, keep it cold while working, handle it gently when wrapping the molds, and allow the baked shells to cool fully before removing them from the molds to help prevent cracking.