Slow cooker lasagne - Good Food Middle East

Ingredients

• 2 tsp rapeseed oil
• 2 onions, finely chopped
• 4 celery sticks (about 175g), finely diced
• 4 carrots (320g), finely diced
• 2 garlic cloves, chopped
• 400g lean (5% fat) mince beef
• 400g can chopped tomatoes
• 2 tbsp tomato purée
• 2 tsp vegetable bouillon
• 1 tbsp balsamic vinegar
• 1 tbsp fresh thyme leaves
• 6 wholewheat lasagne sheets (105g)
• 400ml whole milk
• 50g wholemeal flour
• 1 bay leaf
• generous grating of nutmeg
• 15g finely grated parmesan