Place the vegetables and sage leaves in a bowl, mix with the oil and salt. Thread the sausage, prunes and vegetables alternately onto the skewers.
To grill the kebabs
Charcoal/gas/electric grill: Cover and grill the kebabs over/on a medium heat (approx. 200 °C for approx. 15 mins., turning occasionally.
Combine the mustard with all the other ingredients up to and including the salt, serve with the kebabs.