Heat oil in a large saucepan. Add onion and sauté for 2 minutes, stirring occasionally. Add carrot, celery, mushrooms and cook for 2 minutes. Pour in Leggo's Pasta Sauce and undrained Edgell Brown Lentils, stir well and simmer for 5 minutes.
Meanwhile, toss ½ a cup of cheese and cornflour together. Heat milk in saucepan, add cheese and stir continuously until sauce thickens.
To assemble lasagne, spread a little of the vegetable mixture over the base of a 20cm x 30cm baking dish. Place a layer of lasagne sheets over sauce.
Cover with approximately 1 cup of vegetable mixture, drizzle with ½ cup of white sauce and cover with a layer of lasagne sheets. Repeat twice.
Pour over remaining vegetable mixture and white sauce. Sprinkle with remaining cheese. Bake in a preheated oven at 180°C for 25-30 minutes.