Bring a large pot of water to a boil and cook 12 ounces bucatini according to package directions until just al dente. Reserve 1 cup of pasta water and set aside. Drain the pasta.
In a large skillet over medium heat, add 6 ounces butter and 3 cloves minced garlic. Cook the garlic for 1-2 minutes until fragrant, then add ¼ cup miso and the pasta water. Whisk the sauce until smooth.
Add the cooked pasta to the skillet with the sauce, along with ¾ cup grated Parmesan. Toss the pasta in the sauce until evenly coated. Serve immediately and garnish with furikake or nori flakes if desired.
Notes
Leftover InstructionsFridge: Store leftovers in an airtight container in the fridge for up to 5 days. Add a splash of broth, water, or milk when reheating to keep the pasta creamy.