Low-fat beef and ricotta lasagna

Low-fat ricotta cheese is the secret to giving this lasagna a cheesy taste with a lot less calories.   Ingredients (serves 8): 800g lean beef mince 2 zucchini (baby marrow) 2 carrots 250g mushrooms, chopped 2 garlic cloves, crushed, 700ml tomato pasta sauce ½ cup water 5 fresh lasagna sheets (whole wheat if possible) 250g pkt…