In order to exchange courses with other European universities, we have experimented double blended learning for our master courses (MALTT) in TECFA. It consists of full distance learning combined with blended learning (a course involved of learning both at presence and in distance). After the course, interviews of both the students and the teaching staff were conducted and analysed, which helps to extract the key issues in the design of this course. These issues include the community building, the monitoring of distance students' activities during the course and the task repartition between the teacher and the teaching assistant.