Preheat oven to 180°C.
Add the cooked spaghetti to a large oven-proof skillet. Cut off the top of the brie and then place on top of the spaghetti. Bake for about 25 minutes until the brie is totally melted throughout.
Fold brie into the spaghetti using tongs. Add olive oil, garlic and chilli flakes, and toss until fully coated. Serve with freshly grated Parmesan, if desired. Serve immediately.