Grate the Parmesan cheese and set aside. Mince the garlic and chop the basil.
In a large pot, melt 4 tablespoons of butter over medium heat. Add garlic and cook until fragrant.
Add the vegetable broth and cream, then bring to a simmer. Stir in black pepper and red pepper flakes.
Add spaghetti and simmer until pasta is al dente, stirring occasionally.
Remove from heat and stir in remaining butter until melted.
Gradually stir in Parmesan cheese until creamy.
Garnish with fresh basil and serve immediately.
Notes
To prevent the sauce from being grainy, let the dish cool slightly before adding cheese. Adjust seasonings according to taste. Store leftovers in the fridge for up to 3 days.