Bring a pot of salted water to a boil and cook the pasta until about two minutes before al dente. Reserve some pasta water before draining the pasta.
Heat a small amount of oil in a pan over medium heat. Add the sausage and cook while breaking it apart until browned and fully cooked and remove from the pan.
Add the diced onion and minced garlic to the same pan and cook until softened and fragrant.
Stir in the gochujang and cook briefly until it darkens slightly and starts to release some of its oils.
Pour in the heavy cream and season with salt and black pepper.
Stir until the sauce thickens slightly and turns smooth.
Add the pasta, reserved pasta water, and cooked sausage back into the pan.
Toss continuously until the sauce becomes silky and coats the pasta evenly.
Transfer to bowls and garnish with parmesan and chives if desired.
