Put the lentils and Ballymaloe 100 Recipe Sauce in a large, heavy-based saucepan or casserole on a medium heat. | Add a splash of water to the empty jar and swish it around to catch all the sauce still clinging to the sides, then pour it into a measuring jug. | Boil the kettle and pour enough just-boiled water into the measuring jug to bring it up to 1.2 litres. Add that to the pan too with the stock cubes and stir to combine. Add in the Parmesan rind (if using) and season to taste. | Bring to a boil, then partially cover the pan or casserole with a lid, reduce the heat to medium and simmer for about 30 minutes, until the lentils are soft. | Add the pasta, cover the pan with a lid and cook, stirring occasionally, for 15 minutes, until the pasta is cooked and everything has thickened. | Taste and adjust the seasoning if needed.