Preparation Cook spaghettini in a large pot of boiling salted water, stirring occasionally, until al dente; drain, reserving 3 Tbsp. pasta cooking liquid. Meanwhile, cook anchovies, garlic, red pepper flakes, 1 cup oil, and a pinch of salt in a large skillet over medium-low heat, stirring occasionally, until anchovies dissolve and garlic is tender, 6–7 minutes (do not brown). Stir in parsley, then remove from heat. While anchovy sauce is cooking, heat remaining 3 Tbsp. oil in a small skillet over medium. Add panko and cook, stirring often, until golden, about 5 minutes. Season with salt and pepper, then transfer to paper towels to cool. Return pasta to pot. Stir in reserved pasta cooking liquid, then anchovy sauce and half of the panko mixture. Cook over medium, stirring constantly, until heated through, 1–2 minutes; season with salt and pepper. Serve topped with Parmesan and remaining panko mixture.