DO-AHEAD TIP: Cook and slice sausages.
Place lentils and bay leaf in a large saucepan with a tight-fitting lid; cover with cold water. Bring to a boil then reduce heat,
cover and simmer for 30 minutes. Drain, remove bay leaf and set aside.
Heat the olive oil in a large skillet over medium heat. Add onion, carrot and celery; sauté for 10 minutes or until softened.
Add cooked lentils along with remaining ingredients (tomato sauce through sausages); bring to a boil then reduce heat and
simmer for 10 minutes. Serve hot.