Boil the noodles: Bring a large pot of salted water to a boil. Add the egg noodles and cook according to the package until just tender.
Reserve about 1/4 cup of the pasta water, then drain.
Melt the butter: In the same pot or a large skillet over low heat, melt the butter. If using garlic, add it and cook for 30–60 seconds until fragrant. Don’t brown it.
Combine: Add the cooked noodles back to the pot with the butter.
Toss gently to coat.
Loosen the sauce: Add 1–2 tablespoons of pasta water and toss again. This helps the butter coat the noodles evenly and prevents dryness.
Season: Sprinkle in the Parmesan, a pinch of salt, and black pepper. Toss until the cheese melts slightly and the noodles look glossy.
Finish and serve: Stir in parsley if you like.
Taste and adjust seasoning. Plate immediately while hot.
Optional upgrades: Add red pepper flakes for heat, lemon zest for brightness, peas or spinach for color, or sliced grilled chicken for protein.