1. Bake the sweet potatoes in an oven on 350 F for 25 minutes.
2. Heat the oil in a pan and fry onion and garlic until light brown.
3. Add the barley and 325 ml boiling water. Simmer uncovered for till barley absorbs the water. Keep it aside to cool.
4. Cut sweet potato and apple into small pieces and add to the cooled barley.
5. Mix lemon juice, honey, and balsamic vinaigrette and pour over barley.
6. Top with mixed greens.
7. Serve chilled.