In a medium bowl, toss together onion slices, capsicum slices, mushrooms, canola oil, salt and pepper. Place vegetables in Zone 1 drawer (without crisper plate), then insert drawer in unit.
Insert a crisper plate in Zone 2 drawer and add sausages, then insert drawer in unit.
Select Zone 1, select AIRFRY, set temperature to 195°C and set time to 30 minutes. Select Zone 2, select AIRFRY, set temperature to 195°C and set time to 20 minutes. Press the START/PAUSE button to begin cooking.
When the Zone 1 time reaches 10 minutes, press START/PAUSE, remove drawer from unit and toss vegetables. Reinsert drawer and press START/PAUSE to resume cooking.
When Zone 1 time reaches 10 minutes, press START/PAUSE to pause cooking. Remove drawer from unit and toss vegetables again. Reinsert drawer and press START/PAUSE to resume cooking.
When Zone 2 time reaches 0, remove sausages from drawer and allow them to rest on a serving dish.
When vegetables are complete, remove drawer from unit. Divide the onion, peppers and mushrooms between the buns, then top with sausages and mustard, if desired. Serve warm.
