Toast the breadcrumbs: Heat the oil in a 12-inch skillet over low heat. Add the panko and toast until golden, stirring occasionally, about 4 minutes, Season with flaky salt and set aside.
Cook the pasta: Bring a large pot of water to a boil. Add 2 tablespoons of the salt and return to a rolling boil. Cook the pasta until al dente according to package directions.
While the pasta cooks, prepare the sauce: Heat a 12-inch skillet and toast the walnuts over medium heat, about 4 minutes. Remove and set aside. Wipe out the skillet.
Heat the olive oil in the skillet over medium-high heat. Add the garlic and cook until lightly golden, about 2 minutes. Stir in the anchovies and cook until they melt, about 2 minutes.
Add the red pepper flakes and cook 1 minute more.
Scoop the pasta directly into the skillet and toss with the anchovy mixture. Toss in the walnuts and parsley and mix together until everything is combined, adding ¼ cup of pasta water or more (up to 1 cup), as needed to loosen up the sauce.
Plate in bowls and top with the breadcrumbs. Season with salt and black pepper, if desired. Pass the Pecorino Romano at the table.