01 - Bring a large pot of generously salted water to a rolling boil. Add the mafaldine and cook according to package directions until al dente. Before draining, reserve 1/2 cup of the starchy cooking water.
02 - During the last 3–4 minutes of the pasta's cooking time, add the broccoli florets directly to the boiling pasta water to blanch until crisp-tender. Drain the pasta and broccoli together in a colander.
03 - In a large skillet set over medium heat, warm the olive oil and butter together until the butter melts and begins to foam. Add the minced garlic and chili flakes if using, sautéing for about 1 minute until fragrant but not browned.
04 - Add the lemon zest, lemon juice, blanched broccoli, and drained mafaldine to the skillet. Toss everything together thoroughly, then sprinkle in the grated Parmesan while stirring continuously until a silky, cohesive sauce forms. If the pasta appears dry, incorporate the reserved cooking water a splash at a time to reach the desired consistency.
05 - Season generously with salt and freshly ground black pepper to taste. Remove from heat and fold in the chopped parsley.
06 - Transfer to warm serving plates immediately. Garnish with additional grated Parmesan and a scattering of fresh lemon zest if desired.