Cheesy tuna pasta bake

Ingredients

• 120g dried wholewheat penne
• 2 teaspoons olive oil
• ½ medium onion, finely sliced
• 1 clove garlic, finely diced
• 1 x 400g can chopped tomatoes
• 1 x 160g tinned fish, eg tuna in spring water, drained and flaked
• Handful fresh basil, chopped
• 160g fine green beans, trimmed and cut in half
• 1 x 198g can salt-free sweetcorn, drained (or 160g frozen sweetcorn)
• Freshly ground black pepper, to taste
• 20g reduced-fat mature Cheddar cheese, grated
• 30g wholemeal breadcrumbs
• 1 teaspoon dried oregano
• 160g mixed salad leaves
• 2 teaspoons balsamic vinegar