Preheat oven to 180°C. Grease a 6cm deep, 24cm square baking dish.

Melt butter in a heavy-based saucepan over medium heat. Add flour. Cook, stirring constantly, for 2 minutes, or until bubbly. Remove from heat. Slowly add milk, stirring constantly until well combined. Return to heat. Cook, stirring, until sauce comes to the boil. Mix in gravy until combined. Add 1 1/2 cups of cheese. Stir to combine.

Arrange one-third of potatoes, overlapping slightly, over base of baking dish. Sprinkle with parsley and season. Spoon one-third of the gravy cheese sauce over potatoes. Repeat twice. Sprinkle with remaining cheese and parsley. Bake for 1 hour, or until potatoes are tender and top is golden. If top begins to brown too much, cover with foil. And serve.