Preheat the oven to 160°C. Combine the ricotta cheese, yoghurt and half of the Parmesan cheese in a small bowl. Place a brinjal slice on a work surface and top with a little of the ricotta mixture and a spoonful of the mushroom and lamb mixture. Roll up to enclose filling. Spread the remaining tomato sauce on the base of an ovenproof dish and place the brinjal roll on top. Repeat with remaining brinjal slices and place in a single layer in the baking dish. Sprinkle the remaining Parmesan cheese over the brinjals. Bake for 15 – 20 minutes. Top with fresh herbs, if desired, before serving.