Instructions
1 Heat oil in a large saucepan over a medium-high heat. Cook onion, carrots, celery and capsicum for 5-7 minutes until vegetables start to soften. Add oregano, garlic and chilli flakes. Cook, stirring, for about 1 minute until fragrant.
2 Add tomato paste, tomatoes and 1/2 cup cold water. Bring to the boil. Reduce heat to medium-low. Simmer, uncovered, for 15 minutes until vegetables are cooked through and sauce thickens. Add basil, spinach and beans. Cook, stirring, for about 1 minute until heated through.
3 Meanwhile, combine milk and 1 cup cold water in a medium-sized saucepan. Bring to the boil over a medium-high heat. Slowly pour in polenta, stirring constantly. Reduce heat to medium-low. Cook, stirring, for 2 minutes until thickened. Remove from heat and stir in lemon zest. Stand for 2 minutes until thickened slightly.
4 Preheat grill to high. Spoon bean mixture into 4 x 2-cup-capacity ovenproof dishes (or an 8-cup-capacity ovenproof dish). Top with polenta. Sprinkle with parmesan. Grill for 5 minutes until cheese melts and starts to brown.