1.Preheat oven to 200°C/180°C fan-forced.
2.Cook pasta in large saucepan of boiling water until tender; drain.
3.Heat a third of the butter in large frying pan; cook chicken, in batches, until cooked through. Remove from pan.
4.Heat remaining butter in same pan; cook mushrooms, stirring, until tender. Add flour; cook, stirring, 1 minute. Gradually stir in milk over medium heat until mixture boils and thickens. Stir in chicken, ¼ cup of the romano, ¾ cup of the cheddar and the asparagus. Season to taste.
5.Combine chicken mixture and drained pasta in 2.5 litre (10-cup) ovenproof dish; sprinkle with remaining cheeses. Bake in oven about 15 minutes or until top browns lightly. Serve pasta bake sprinkled with parsley.