Mary Berry's butternut squash lasagne recipe is a quick and easy dish that's ideal for vegetarians. A lasagne with wow factor - the secret ingredient is butternut squash. Prepare the dish the day before if you can, so the lasagne sheets have time to soften in the sauce. This recipe is sure to become a family favourite. This vegetarian lasagne serves 6 people and takes about 1hr and 15 mins to prepare and cook. Mary Berry's butternut squash lasagne recipe shows you how to make a rich, white sauce infused with mustard from scratch. Serve with salad and crusty bread. If you want to make this dish suitable for meat-eaters add minced beef, pork or turkey to the mix - you might have to make a little extra tomato sauce so it covers all the meat.