Cook the barley in salted boiling water.
Drain and run under tap water to stop the cooking.

Heat a griddle. Meanwhile finely slice the zucchina, the eggplant, the onion and the champignons. Brush the griddle with olive oil and grill the veggies for a few minutes on both sides, until grill marks appear.

In a small bowl mix 3 tablespoons of olive oil with finely sliced garlic, 1 tablespoon of balsamic vinegar and 1 teaspoon of salt, 1 teaspoon of mustard and a pinch of freshly ground black pepper then whisk well until combined.
If the sauce is too thick add some olive oil.

Mix well the barley with the veggies and the sauce and put in the fridge.
Take it out from the fridge 15 minutes before serving.

Did I mention cold beer?