Heat oil in a large saucepan over high heat. Add onion and garlic, cook for 2-3 minutes or until softened. Add beef mince and cook for 5 minutes or until browned, breaking up any large pieces.
Add tomatoes, Leggo's Tomato Paste, stock and herbs, including bay leaf. Cover and simmer for 15 minutes, stirring occasionally. Remove bay leaf.
To make cheese sauce: Melt butter in a saucepan, add flour and stir continuously for 1-2 minutes without browning. Remove from heat and gradually stir in milk. Bring to the boil stirring continuously until sauce thickens. Add cheese and stir until cheese melts.
Grease a 25 x 30cm baking dish. Cover with a layer of lasagne, spread with a 1/3 of the meat sauce and sprinkle with 1/3 of the mozzarella cheese. Repeat to make 2 more layers. Finish with a layer of lasagne sheets. Pour cheese sauce over the top.
Cover with foil and bake in a preheated oven at 180°C for 20 minutes, remove foil and cook a further 10 minutes or until heated through and cheese sauce is a light golden brown.