Ratatouille Risotto

Name: Ratatouille Risotto
Ingredients: 2 tbsp oil, (divided); 1 medium onion, (diced); 1 small aubergine ((eggplant), cut into 1cm dice); 1 bell pepper, (diced (I used orange)); 1 medium courgette ((zucchini), cut into 1cm dice); 4 medium mushrooms, (diced); 3 cloves garlic, (minced); 2 tsp dried oregano; 250 g (~ 1 1/4 cups) arborio rice; 1 litre ((~ 4 cups) vegetable stock); 3 tbsp tomato puree; 1 tbsp balsamic vinegar; 1 tbsp basil pesto ((use vegan pesto if needed)); To serve: fresh basil ((optional))