Heat the oil in a large deep ovenproof frying pan.
Cook the onion, garlic, carrots, zucchini, celery and thyme, stirring for 10 minutes or until browned.
Add the mince and and cook until browned, breaking up any large lumps.
Stir in the tomato and water. Season with salt and pepper and bring to the boil.
Break up the lasagne sheets and push them into the beef mixture, making sure they are covered.
Reduce the heat and cook for 15 minutes or until the pasta is tender and the sauce has thickened.
Top with grated cheese and place under the grill until the cheese is golden.