1. Cook rigatoni in salted boiling water until al dente (about 10-15 minutes). Reserve ½ cup pasta water before draining.
2. Cut pork belly into 1-inch pieces and brown in a pan over medium heat for 3-5 minutes per side until crispy. Remove pork but leave about 1 tablespoon of rendered fat in the pan.
3. Add sliced garlic to the fat and sauté for 30 seconds until fragrant.
4. Stir in gochujang and cook for about 1 minute to release aromas and deepen flavor.
5. Pour in milk, heavy cream, and soy sauce, then simmer for 3 minutes until slightly thickened. Keep sauce on low heat if pasta is not ready.
6. Return cooked rigatoni, pork belly, and reserved pasta water to the sauce. Simmer over medium heat, stirring frequently, for 2-3 minutes until the sauce coats the pasta well and reaches desired consistency.
7. Remove from heat and, if desired, top with grated parmesan cheese and chopped chives or green onions before serving.