Butternut Squash Lasagne (v)

Serves 6

Make the day before

1tbsp olive oil
225g butternut squash, peeled and chopped
1 red pepper, halved, deseeded, and diced
1 onion, peeled and roughly chopped
2 garlic cloves, peeled and crushed
225g chestnut mushrooms, sliced
2 x 400g cans chopped tomatoes
1tbsp tomato puree
2tsp sugar
1tbsp freshly chopped thyme
salt and pepper, to season
100g spinach, chopped
6-8 sheets lasagne

White sauce
75g butter
75g plain flour
900ml hot milk
2tsp Dijon mustard
100g Gruyere cheese, grated
250g mozzarella, chopped into small cubes

Heat the oil in a large pan.  Add the squash, pepper, onion and garlic and fry over a moderate heat for 4-5 mins or until the onion is softening.
Add the mushrooms, tomatoes, puree, sugar and thyme, then season.  Cover and simmer over a low heat for 20-30 mins or until the vegetables are tender.  Add the spinach and toss together until just wilted.
Meanwhile, make the white sauce.  Melt the butter, add the flour and stir over the heat for 1 min.  Slowly whisk in the milk until the sauce is smooth and thick.  Season, then stir in the mustard and 1/2 the Gruyere.
Spoon 1/3 of the tomato sauce over the base of the ovenproof dish, then spoon 1/3 of the white sauce on top.  Arrange a single layer of lasagne on top and scatter over 1/2 the mozzarella.
Spoon on 1/2 the remaining tomato sauce, followed by 1/2 the rest of the white sauce.  Add another layer of lassagne and scatter over the remaining mozzarella.  Spread the remaining tomato sauce on top, followed by the rest of the white sauce, then sprinkle with the remaining Gruyere.
Transfer to the fridge for at least 6 hrs or overnight, so the lasagne starts to soften.
To serve, preheat the oven to 200, gas mark 6.  Then bake for 45 mins or until golden and bubbling around the edges.