Bring 3½ cups (830 ml) of water to a boil. Add salt and ½ teaspoon of oil. Add pasta and cook for 8 to 10 minutes until just tender. Drain and set aside.
Heat 1 tablespoon (14 g) of butter in a pan over medium heat. Add chopped garlic and cook for 1 minute.
Add onion and cook for 1 minute. Add capsicum, yellow bell pepper, carrot, and corn. Cook on low heat for 3 to 4 minutes, keeping a little crunch. Remove veggies and set aside.
In the same pan, add the remaining 1 tablespoon (14 g) of butter. Add flour and cook on low heat for 30 seconds, stirring.
Add milk slowly, a little at a time, stirring the whole time to keep the sauce smooth.
Cook on low heat for 4 to 5 minutes, stirring often, until the sauce thickens and coats the back of a spoon.
Add grated mozzarella and stir until fully melted.
Add drained pasta and mix to coat. Add the cooked veggies, black pepper, oregano, chilli flakes, and salt. Mix well.
Cook on low heat for 1 to 2 minutes. Serve hot.