First make the aubergine puree. Spray an aubergine with low calorie cooking spray, season and wrap in foil. Place in the oven for 20-30 minutes then scoop out the insides and mash it up.
Heat a pan and spray with low calorie cooking spray.
Add the onion, celery, carrots and garlic to the pan and cook for a few minutes, until they start to soften.
Add the mince and cook until it starts to brown. Add the herbs and Worcestershire sauce, continue to cook for a few more minutes.
Add courgette, peppers, mushrooms and fry for about 5 minutes then stir in the aubergine puree.
Add the chopped tomatoes, stock cube and tomato puree. Add 200ml (just under 1 cup) water and stir well. Put the lid on the pan and simmer for 20-30 minutes. Adjust seasoning if necessary.
Spread a layer of the mince mixture on the bottom of a decent sized oven proof dish, then add a layer of Butternut Squash Lasagne sheets, then repeat until you reach the top of the dish, ending with a layer of lasagne sheets. make sure you leave enough room for the sauce
Mix the yogurt, eggs, mustard powder and salt to taste. Beat well to make sure it's mixed properly.
Cook in the oven for 45 minutes, on 190-200°C.
Remove from the oven and allow to rest for 5-10 minutes, so it is easier to portion.