In a large pot or deep skillet, combine the dried penne pasta, broccoli florets, water, olive oil, sliced garlic, salt, black pepper, and red pepper flakes.
Bring the mixture to a boil over medium-high heat, stirring occasionally to prevent the pasta from sticking.
Once boiling, reduce the heat to medium and continue to cook, stirring frequently, until the pasta is al dente and the water has mostly evaporated, about 12 to 15 minutes.
Remove the pot from heat and stir in the grated Parmesan cheese and chopped fresh parsley until well combined.
Adjust seasoning with additional salt and pepper if desired.
Serve immediately, garnished with extra Parmesan and parsley if preferred.