Fill a large saucepan with 1 inch of water and fit with a steamer basket. Bring to a simmer. Place the potatoes in the steamer basket and cook until tender, 12 to 14 minutes. Add the asparagus to the steamer basket during the last 3 minutes and steam until tender. Transfer the potatoes and asparagus to a large bowl. Toss with the oil, vinegar, mustard, and ¼ teaspoon each salt and pepper.
Heat grill to medium. Season the chicken with the coriander, ½ teaspoon salt, and ¼ teaspoon pepper. Grill until cooked through, 2 to 4 minutes per side. Serve the chicken with the vegetables.