Pan-fry pork belly until cooked through. Cut into smaller chunks, season lightly with salt, and set aside.
Add pasta to salted boiling water.
While the pasta is cooking, melt butter in a pan and sauté garlic and ssamjang. Add cream, stir together, and simmer over medium heat for 3 minutes. Add pork belly to reheat.
Once pasta is al dente, reserve about 1 cup of pasta water before straining. Add pasta to sauce and mix in parmesan cheese, red pepper flakes, and pepper. Slowly drizzle in pasta water until the sauce is silky.
Season with salt if necessary. Top with more parmesan cheese, green onions, and a soft boiled egg.