Preheat oven to 180°C/160°C fan-forced. Heat 1 tablespoon oil in a large frying pan over medium heat. Brown pork in batches. Transfer to a bowl.
Add onion and chilli flakes to pan and cook, stirring often, over medium heat for 3-4 minutes or until softened. Sprinkle flour over onion mixture and stir until combined. Cook, stirring, for 1 minute. Stir in tomato paste and cook, stirring, for 1 minute.
Gradually add water, stirring constantly, until combined. Stir in tomatoes. Bring mixture to the boil. Stir through pork. Transfer mixture to an 8-10 cup (about 8cm deep) baking dish.
Arrange potato slices, overlapping slightly, over casserole. Brush with remaining olive oil and cover loosely with a sheet of baking paper then foil. Bake for 1 hour or until pork is tender. Sprinkle parmesan over potatoes and cook, uncovered, for 25-30 minutes or until golden. Serve with crusty bread