Most constructionist efforts have focused on supporting learners with tools for designing with digital and/or physical media. Recent developments in life sciences now allow K-12 learners to design with living materials, or to biodesign. In this paper, we report on the development of a biodesign studio activity called biocakes wherein teams of high school youth genetically modified a yeast strain to bake a nutrient fortified food product. Using a qualitative deductive analysis of classroom observations, interviews and projects, we examined high school youth experiences and reflections of these activities to answer three research questions: (1) What kind of artefacts did youth make with living media? (2) How did youth engage in biodesign? and (3) What did youth have to say about their biodesign experiences? We discuss how our analyses of biodesign applications highlight the importance of assembly practices, social engagement and imaginative design for constructionist learning. These insights provide compelling examples for designing with living media in K-12 education.