Welsh Beef lasagne

Ingredients

• 450g lean PGI Welsh Beef mince
• 1 large onion, chopped
• 2 garlic cloves, crushed
• 2 celery sticks, finely chopped
• 2 red peppers, finely chopped
• 2 carrots, grated
• 400g tin of chopped tomatoes
• 2 tbsp tomato puree
• 150ml beef stock
• 1 tsp mixed herbs
• Seasoning
• 50g unsalted butter
• 50g plain flour
• 500ml whole milk
• 1 tsp Dijon mustard
• 100g mature Welsh cheddar cheese, grated
• 12 lasagne sheets