Preheat oven to 180 / 160 C fan. Cut off the top rind of brie then place brie in a cast iron pan of about the same size - you want the brie to fit snugly into the pan. Bake until the brie is totally melted throughout, about 30 minutes.
Meanwhile, cook spaghetti according to packet instructions. When cooked, drain and save about 200ml pasta water, then transfer the cooked spaghetti to a warmed bowl.
In a large saucepan, fry the pancetta in 1 tbsp of the olive oil until golden and crisp, then add the garlic and fry for a further 1 minute. Add to the bowl with the pasta and toss with the spaghetti, the remaining 1 tbsp olive oil, parsley, chilli flakes and plenty of freshly ground black pepper.
After removing brie from oven, immediately add spaghetti to the cheese and toss until coated using tongs. If the brie is too thick, add a little pasta water to loosen. Serve immediately with Parmesan.
The melted brie will congeal very quickly once removed from the oven. It’s best to eat this dish immediately after it's been made.