2. While the sausages are roasting, whisk together remaining olive oil, balsamic vinegar, brown sugar, and grainy mustard and season to taste with salt and pepper. Toss with cooked barley and let sit at room temperature.
3. When the sausages are fully cooked remove them from the oven and let them rest for 5 minutes. Scatter the arugula over a platter and drizzle with olive oil. Toss barley on top of arugula then top with sausage and toasted bread. Top with parsley and serve with grainy mustard.