01 - Bring a large pot of generously salted water to a rolling boil. Add the mafaldine and cook according to package directions, subtracting 2 minutes from the recommended time so the pasta finishes in the sauce.
02 - Three minutes before the pasta is done, add the broccoli florets directly to the boiling pasta water. Reserve 1/2 cup of the starchy cooking water, then drain the pasta and broccoli together in a colander.
03 - While the pasta cooks, warm the olive oil in a large skillet over medium heat. Add the sliced garlic and chili flakes if using, and sauté for 1 to 2 minutes until fragrant and just beginning to turn golden, careful not to brown.
04 - Transfer the drained mafaldine and broccoli into the skillet. Pour in the lemon juice and scatter the zest over the top. Add a splash of the reserved pasta water and toss vigorously, adding more water as needed to create a silky, emulsified sauce that coats every ribbon.
05 - Sprinkle the grated Parmesan over the pasta and toss until the cheese melts into the sauce and clings to the noodles. Season with salt and freshly ground black pepper to taste.
06 - Divide among warmed plates immediately. Shower with extra Parmesan and scatter fresh basil or parsley over each portion if desired. Serve right away while hot.