- With the rack in the middle position, preheat the oven to 200 °C (400 °F). Butter a 33 x 23-cm (13 x 9-inch) or 3 litres (12 cups) capacity baking dish.
- In a large pot of salted boiling water, cook the pasta until al dente. Drain and oil lightly. Set aside.
- Meanwhile, in a large non-stick skillet, brown the turkey cubes, half at a time, in 30 ml (2 tablespoons) of the butter. Season with salt and pepper. Deglaze with the lemon juice. Set aside in a large bowl.
- In the same skillet, brown the mushrooms and onion in 60 ml (1/4 cup) of the butter. Season with salt and pepper. Sprinkle with the flour and cook for 1 minute, stirring constantly. Add the milk and broth and bring to a boil, stirring constantly. Add the peas, 250 ml (1 cup) of Parmesan cheese and the nutmeg. Adjust the seasoning.
- Pour the mushroom sauce over the turkey cubes. Add the pasta and stir to combine. Spoon into the baking dish.
- In a microwave, melt the remaining butter. In a bowl, combine the bread with the remaining cheese and the melted butter. Sprinkle over the pasta. Bake for about 25 minutes.