16 ounces spaghetti, linguine or bucatini
6 tablespoons unsalted butter
3 tablespoons white (or red) miso
4 ounces Parmesan, finely grated (1 packed cup)
Kizami nori, furikake or thinly sliced seaweed snacks, for garnish (optional)
Bring a large pot of salted water to a boil. Add the pasta and cook, stirring occasionally, until al dente. Reserve 1 1/2 cups pasta water, then drain the pasta.
Add the butter, miso and 1 1/4 cups pasta water to the pot and whisk over medium heat until miso breaks down and liquid is uniform, 1 to 2 minutes. Add the pasta and Parmesan and cook, stirring vigorously with tongs until cheese is melted and sauce emulsifies. (The key word here is “vigorously.” To achieve a silky smooth pasta instead of a gloppy one, put your cacio e pepe skills to work.)
Divide among shallow bowls and sprinkle with nori or furikake, if using.