Lasagne Stuffed Zucchini Boats with Salad

• 4 zucchinis, sliced in half lengthways
• 2 tbsp extra virgin olive oil
• 1 small brown onion, diced
• 300 g lean mince
• 400 g tin crushed tomatoes
• 1 tsp oregano
• 1 cup ricotta
• 2 spring onions, thinly sliced
• 2 cup mixed leaves
• 1 tbsp balsamic vinegar