Cook the meat, onions and mushrooms in saucepan until cooked then drain the oil.
Mix the tomato paste, meat, mushroom and onion together in large bowl or saucepan then add the garlic.
Make the white sauce and have ready to the side.
Place a thin layer of white sauce down into the bottom of the lasagne; then place a layer of lasagne sheets down; then cover with the meat sauce; then cover with a layer of cheese and then pour some white sauce over the top.
Continue with another layer of lasagne sheets, meat sauce, etc. until you have reached the top.
On the top just place heaps of cheese and the last of the white sauce.
Cook in oven on 200 degrees C for 30 minutes to an hour until golden brown on top and base is soft when serving.