First make the Béchamel. To do this, melt the butter in a large saucepan on a medium to low heat until it bubbles. Add the flour and stir through for a couple of minutes. Add about a ¼ of the milk, remove from the heat and whisk vigorously until you have a smooth paste. Return to the heat, slowly adding the rest of the milk and keep stirring. Add the nutmeg and bayleaf and stir until you have a hot, thick sauce. Turn off the heat and stir in the cheese. Taste and season with salt and pepper accordingly. Set aside until needed.
Preheat the oven to 180°C.
For the filling, heat the butter in a large frying pan on a medium to low heat. Fry the garlic and mushrooms until beginning to brown at the edges. Remove from the heat. Remove and discard any skin and bones from the chicken and chop into bite-sized pieces. Spoon 1/3 of the Béchamel sauce into a small saucepan and remove the bayleaves. Butter an oven-proof lasagne dish. Return both pans of sauce to the heat, stir in the chicken and mushrooms to the bigger pot, adding a little more milk to loosen if needed and tasting for seasoning.
Spoon half the chicken and mushroom mixture into the lasagne dish, cover with one layer of lasagne sheets and repeat. Pour over the plain Béchamel and spread evenly. Sprinkle over the Parmesan and bake in the oven for 30 minutes or until golden and bubbling. Serve with French beans and broccoli.
*This dish is very indulgent so shouldn't be eaten too often. But it's perfect for those special occasions!
Freezing and defrosting guidelines
Once the dish has cooled completely, transfer it to an airtight, freezer-safe container, seal and freeze for up to 1-3 months. To serve, defrost thoroughly in the fridge overnight before reheating. Loosely cover with foil and bake until dish is thoroughly heated through. Reheat until piping hot.
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.