The rapidly growing popularity of Christian Seders in recent years has been accompanied by the equally rapid emergence of a genre of “how-to” guides that tell celebrants, among other things, how to structure their evenings – what to do and when – and how Jesus is supposed to be understood to have fulfilled the hopes and promises embedded in the Seder and Haggadah. This paper positions the genre as a social phenomenon tied to a process of authentication, through which Christian Seders are simultaneously re-positioned as a form of authentically Christian practice and legitimized as such over and against ongoing critiques that the practice is an appropriative and supersessionist one. The paper maps and discusses recurring elements in the guides and analyzes their shared symbols, ideas, and objects to highlight the major constituent parts of supersessionist rhetorics of authenticity about Christian Seder practices. Using a critical form of social semiotics, the analysis highlights how guide-authors navigate both the modal affordances of traditionally Jewish practice and narrative and an historically Christian epistemological framework in their commitment to suturing them into a newly-fabricated and artificially-aged whole. This suturing is an appropriative process that often requires overexplicit Christian or Christianizing anchoring of core semiotic resources for Christian Seders to be legitimized. As historically conceived, neither Seders nor, for example, the conception of Jesus as the Paschal lamb or as Jewish, allow for easy cross-cultural translation; both modalities need to be actively shaped for any claim that they are related to be made. This shift, or suturing, may entail linking the New Testament last supper to the Passover meal or convincing readers how an element of the Seder should be understood to symbolize something Christian, often Easter-related. This is neither a neutral nor self-evident reframing of the Seder; how-to guides allow socially situated, often but not exclusively white US American Evangelical Protestants, to name and claim a Jewish practice as their own in a dual sense: on the one hand, they demonstrate the practice for newcomers and, on the other, justify, legitimize, and mark it as authentic.