Boil pot of water and salt generously. The general rule of thumb is 1 tablespoon of salt for 1 lb of pasta. Since we are using ½ lb of pasta, salt water with ½ tablespoon of salt. Cook rigatoni according to package instructions.
In a pan, melt 1 tablespoon of unsalted butter on low-medium heat and add minced garlic. Lightly sauté for 30 seconds until fragrant.
Add gochujang and cook down for about a minute to release the paste's flavors. Next, add heavy cream and gently stir until gochujang is evenly distributed throughout and cream becomes a rose-pink color.
Drain pasta and reserve ½ cup of the pasta water. Add reserved pasta water into the creamy gochujang sauce and bring the sauce back to a gentle simmer.
Add cooked pasta into sauce and mix until pasta is evenly coated. Simmer at low heat for about 2-3 minutes.
Finish off with parmesan and the last 1 tablespoon of butter to keep sauce shiny and glossy. Stir gently until butter has melted.
Serve with additional parmesan and chopped chives.