Rinse barley, place in a medium saucepan and cover with 4 cups of water. Lid on, bring to the boil, simmer for 35-40 minutes.
Meanwhile, add onion, celery and garlic to a food processor. Pulse until finely chopped or minced. Heat a medium heavy based saucepan on low. Add evoo, chopped veg and a pinch of salt. Cook over a low-medium heat, stirring occasionally until softened, about 10 minutes.
Strain barley and add to saucepan, stir to coat in oil. Use a microplane to add almost half a freshly grated nutmeg. Add stock, bring to boil and simmer for 10 minutes. Season to taste.
Meanwhile, to make the salad. Toss all salad ingredients gently, season to taste.
To serve, spoon out barley onto a serving platter, top with salad and a little more freshly grated nutmeg. Serves 4.