Lasagne al forno

Ingredients

• 2 tbsp olive oil
• 750 g lean minced beef
• 50 g plain flour
• 2 red onion, roughly chopped
• 3 stalks celery, roughly chopped
• 2 garlic cloves, finely grated
• 2 beef stock cube, make 150ml
• 8 g caster sugar, (1 tsp)
• 2 tbsp tomato purée
• 3 tsp dried thyme
• 800 g can chopped tomatoes
• 50 g butter
• 750 ml full-fat milk, warm
• 2 tsp dijon mustard
• 50 g parmesan cheese, finely grated
• 375 g dried lasagne sheets
• 75 g cheddar cheese, grated