Preheat oven to 400˚F (200˚C). Cook pasta according to package directions. Reserve ½ cup (125 mL) pasta water; drain pasta.
Meanwhile, heat 2 tbsp (30 mL) basil pesto in large, non-stick skillet set over medium heat. Mix in mushrooms, carrots and salt; cook 5 to 8 min. until mushrooms are softened. Add tomato sauce, lentils and 1 cup (250 mL) water. Bring to a boil. Reduce heat to low; simmer 15 to 20 min. or until lentils are tender.
Stir in zucchini and chicken; simmer 10 to 15 min., until zucchini is tender. If sauce is too thick, thin with reserved pasta water to desired consistency. Stir in cooked pasta and remaining pesto.
Transfer pasta mixture to greased 8-in. (20-cm) square baking dish. Dollop ricotta evenly over pasta. Sprinkle with Parmesan. Broil 3 to 5 min. or until top is golden brown.
Alternatively, skip the broiling step and simply toss ricotta with pasta then top with Parmesan before serving.