Ricotta and salami lasagne

Ingredients

• 1 onion, finely chopped
• 1 tablespoon olive oil
• 80 grams sliced salami, chopped
• 1 carrot, diced
• 1 celery stalk, chopped
• 575 grams jar red wine Bolognese pasta sauce
• 2 tablespoons chopped basil, plus leaves to serve
• 2 tablespoons parsley, chopped
• 375 grams lasagne sheets
• 400 grams soft ricotta
• 1 1/2 cup grated mozzarella
• White sauce
• 60 grams butter, chopped
• 1/4 cup plain flour
• 2 cups milk
• 2/3 cup grated parmesan