1. Heat oil in a medium sized heavy based saucepan over medium heat. Add onion, carrot, celery and garlic and sauté until softened.
  2. Add both types of mince, breaking up with a wooden spoon, and fry until browned.
  3. Add milk, tinned tomato, bay leaves and 500ml water and bring to the boil.
  4. Season with salt and pepper, lower heat and simmer for 1.5 hours, stirring occasionally.
  5. Preheat oven to 180C.
  6. Place a ladle of meat sauce in the base of a lasagna tray and place 2 lasagna sheets on top, trimming if necessary.
  7. Place 2 ladles of sauce on top and sprinkle with mozzarella and Parmesan.
  8. Repeat layers three more times, finishing with meat sauce topped with mozzarella and Parmesan.
  9. Cover the lasagna with aluminium foil and place in the oven for 30 minutes.
  10. Increase oven temperature to 200C, remove foil and bake for a further 15 minutes.
  11. Allow lasagna to rest for 15 minutes before portioning and serving.