Soak the Mary Berry's chicken lasagne sheets in water to ensure they cook evenly.
In a frying pan over high heat, add a bit of oil. Sear the chicken thighs until they turn golden brown. Season them with salt, pepper, and thyme for extra flavor.
In a separate bowl, combine the sun-dried tomato paste and tomato paste to create a rich tomato sauce.
Begin assembling the lasagne in an ovenproof dish. Create three layers of chicken mixture, ensuring even distribution.
Add the rich tomato sauce to the layers, enhancing the flavor of the dish.
Prepare a creamy white sauce and drizzle it over the lasagne.
Sprinkle grated cheddar on top for a delightful crust.
Bake the lasagne in the oven until the lasagne sheets turn golden brown and the cheese melts.
Serve your Mary Berry's Chicken and Mushroom Lasagne with a side salad or other accompaniments of your choice.