Sausage and fennel lasagne

Ingredients

• 1 x 250g pack dried lasagne sheets
• 1 x 210g pack mozzarella, drained
• 75g finely grated parmesan
• 1 onion, finely chopped
• 2 cloves garlic, crushed
• 6 tbsp olive oil
• 2 x 400g packs Taste the Difference Sicilian-inspired pork sausages
• 1 tbsp fennel seeds, lightly crushed
• 2 bay leaves
• 125ml red wine
• 3 heaped tbsp tomato purée
• 2 x 400g tins peeled plum tomatoes
• 1 litre milk
• 1 small onion, halved through the root
• ¼ nutmeg, finely grated
• 75g butter
• 75g plain flour