Begin by bringing a large pot of salted water to a boil. Add 8 ounces of long thin pasta and cook according to package instructions until al dente, about 8–10 minutes. Reserve ¾ cup of pasta water, then drain and set aside.

In a small bowl, whisk together the reserved pasta water with 3 tablespoons of white miso paste until smooth. Set aside.

In a large skillet, melt 2 tablespoons of butter over medium heat. Add 1 teaspoon of coarsely ground pepper, stirring continuously for another minute until fragrant.

Pour the miso mixture into the skillet, stirring well. Heat for about 2 minutes. Add the drained pasta and ½ cup of finely shredded Parmesan cheese, stirring until melted and combined.

If the sauce is too thick, gradually add more reserved pasta water to achieve desired consistency, stirring until creamy.

Remove from heat and plate generously. Sprinkle with extra Parmesan, pepper, and optional garnishes like green onions, Thai red chilis, or chili crisp. Serve immediately.