Squash and Fennel Lasagne - River Cottage

Ingredients

• 1kg squash
• 6 tablespoons rapeseed or olive oil, plus extra to trickle
• 1 fat garlic clove, finely chopped
• A few sprigs of thyme, leaves only, finely chopped
• 750g fennel (3 large bulbs)
• 150g blue cheese or goat’s cheese, crumbled
• 125g lasagne sheets (fresh is best, but dried is fine)
• 20g Parmesan, Cheddar or other well-flavoured hard cheese, grated
• Sea salt and freshly ground black pepper
• 1 litre whole milk
• 1 bay leaf
• 1 onion, roughly chopped
• 1 celery stalk, roughly chopped
• A few black peppercorns
• 50g unsalted butter
• 50g plain flour
• 2 teaspoons Dijon mustard