Mathematical reasoning, which plays a critical role in students' capacity to make sense of mathematics, is now emphasised more strongly in various curricula internationally. However, reasoning is sometimes difficult for teachers to recognise, let alone teach. This case study considers video of one teacher's implementation of a problem-solving lesson in a year 1 primary school class in Australia. It examines the opportunities this teacher provided to leverage reasoning and contributes to the body of knowledge on ways reasoning may be elicited during problem solving. The new Eliciting Mathematical Reasoning Framework arising from the analysis of the data in this study builds on and extends previous research. It provides a tool to support researchers, teacher educators, professional learning providers, and teachers in recognising and eliciting reasoning.