To make these Truffle Peanut Butter Brownies 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 check that the cocoa powder, powdered sugar, chocolate chips, peanut butter, baking powder, vanilla, and any packaged ingredients are labeled gluten free, since some brands may vary or be processed in shared facilities. If your gluten-free flour blend does not already contain a binder, you may need to add a small amount of xanthan gum to help maintain the texture of the brownie base. For anyone with celiac disease or severe gluten sensitivity, use clean bowls, mixers, spatulas, pans, parchment, and cutting tools to avoid cross-contact.