Cook asparagus in a large frying pan of simmering water for 2-3 minutes or until just tender. Drain, refresh in cold water and place onto paper towel.
Season chicken with salt and pepper. Wipe the frying pan with paper towel to dry. Add oil to pan and heat over medium-high heat until hot. Add chicken and cook, turning occasionally, for 3-4 minutes or until almost cooked through. Using a slotted spoon, remove to a plate and set aside.
Increase heat to high, add mushrooms and cook, turning occasionally, for 2-3 minutes or until just tender. Add chicken and asparagus and toss gently to combine. Add balsamic vinegar, stir well to combine and cook for 30 seconds.