1. Put the oil into a medium sized saucepan, heat for 15 seconds before adding the chopped onions, sliced mushrooms and herbs.
2. Fry on a low heat for 5 minutes until the ingredients are soft.
3. Add the minced beef to the saucepan and continue to cook until the minced beef is browned all over. This will take approximately 5 minutes.
4. Add the tomato puree and chopped tinned tomatoes to the saucepan and stir well, mixing all ingredients together.
5. Continue to cook until approximately 1/3rd of the liquid has cooked away.
6. Take off the heat and allow to stand while you make the cheese sauce.
7. To make the cheese sauce.
8. Put 2 tablespoons of the milk into a jug and add the cornlour.
9. Mix the milk and cornflour to a paste.
10. Pour the rest of the milk into a small saucepan and heat gently until it is just about to boil.
11. Take the saucepan with the milk in, off the heat and pour in the cornflour and milk paste. Stirring with a wooden spoon all the time.
12. Put the saucepan back onto a gentle heat and bring to simmer. Continue to stir all the time.
13. Take the sauce off the heat and add the grated cheeses.
14. Leave to stand on the side.
15. Put half of the meat mixture into an 8” square dish (that is able to be used in the oven). Spread evenly over the bottom of the dish.
16. Place half the sheets of lasagne over the meat.
17. Place the rest of the meat mixture over the lasagne and then top with the rest of the lasagne sheets.
18. Pour over the cheese sauce and put in the oven for approximately 40-45 minutes.