Put the ginger juice in a small heavy-based saucepan over high heat and bring to the boil. Whisk in the agar. Bring back to the boil, whisking constantly, and cook for 30 seconds. Pour the hot ginger mixture into a container, leave to cool completely, and then refrigerate for 4–6 hours until completely set.
Break up the ginger gel using a hand-held blender and then place in a vita-prep