Mushroom Barley Casserole

Ingredients

• 2 tbsp / 25 ml canola oil
• 1 large onion, chopped
• 4 cups / 1 L sliced mushrooms of your choice
• 1 tbsp / 15 ml balsamic vinegar
• 1 cup / 250 ml pot barley
• 2.5 cups / 625 ml water
• 1 tsp / 5 ml dried thyme
• freshly ground black pepper to taste