Peel and slice onions to about 1/8-inch thick — thin enough to cook quickly, thick enough to avoid scorching. Yellow or Spanish onions work best. Limit to 2 large onions per 12-inch Skillet to prevent steaming. Have your fat ready and keep a splash of water, broth, or wine nearby to deglaze if needed.

Heat a Skillet over medium to medium-high heat. Add butter, oil, or a mix and let it shimmer. Add sliced onions in large handfuls, stirring for 1–2 minutes per batch until they begin to soften — this prevents overcrowding. Once all onions are in, season with a pinch of salt. Cook over medium heat, stirring every few minutes, for 8–12 minutes total until soft, translucent, and lightly golden. To speed up softening, add 1/4 to ½ cup water or broth and cover; steam wilts the onions in a few minutes. Remove the lid once liquid evaporates and continue cooking uncovered. If the pan looks dry, deglaze with a splash of water, broth, or wine, scraping up any browned bits. Don't crank the heat — high heat burns the outside before the onions cook through.

Pour in the 1 cup chicken broth low-sodium and bring to a gentle simmer, scraping up any bits from the bottom of the pan. Add the 1 cup heavy cream and ¼ tsp Italian seasoning (if using), and simmer for 4–5 minutes, stirring occasionally, until the sauce begins to thicken slightly.

Reduce the heat to low and stir in the grated ¾ cup Parmesan cheese freshly grated until fully melted and the sauce is smooth. Season with ¼ tsp black pepper freshly ground and 1 tsp salt for pasta water, plus more to taste. If the sauce is too thick, add a splash of the reserved pasta water to loosen it.

Add the drained 12 oz fettuccine or linguine pasta directly to the Skillet and toss well to coat every strand in the creamy 6 cloves garlic minced sauce. Let it cook together for 1 minute so the 12 oz fettuccine or linguine pasta absorbs the flavors. Serve immediately, garnished with 2 tbsp fresh parsley chopped and extra ¾ cup Parmesan cheese freshly grated.