This paper analyses an experiment in collaboration between the ELP and DELF (official certification in the French language) for students at B2 level. The speaking test is based on the presentation and discussion of the language biography and project work collected in the dossier. The lively interaction between examiner and test taker, as authentic social agents, fulfils the action-oriented approach of the CEFR. The ELP works as a mediation tool for an ethical cooperation between the local educational system and an international agency, promoting both plurilingualism and intercultural dialogue. Most of the literature on portfolios and assessment (review in Quingua 2010) focuses on writing development, while our experiment concerns speaking skills embedded in social interaction with a portfolio-based final test.