Combine the brown gravy mix with 1 cup of cold water in a large measuring cup until smooth. Stir in the tomato sauce and seasonings, then set it aside for later use.

Cut the chicken breasts into evenly-sized cubes, ensuring they cook uniformly. Season generously with salt and pepper, then sprinkle with flour, tossing to coat them nicely.

Heat olive oil in a large skillet over medium-high heat. Add the chicken cubes, searing them for about 3-4 minutes until golden brown. Flip and cook for another 3 minutes until cooked through, then remove from the skillet.

Turn off the heat and pour in 1/4 cup of the white wine, then switch the heat back to medium. Use a silicone spatula to scrape the delicious brown bits from the skillet's bottom.

Add the butter and sliced onions, cooking over medium heat for about 20 minutes until the onions are deeply softened and caramelized, stirring often.

Toss in the minced garlic and cook for an additional minute until fragrant.

Pour in the remaining white wine, letting it bubble gently for about 5 minutes for flavor development.

Slowly add the gravy mixture from step 1 to the skillet. Bring it to a boil, allowing it to thicken for about 30 seconds before reducing to a simmer and adding the chicken back in.

Partially cover the skillet and use this time to boil water for the spaghetti. Once boiling, add a pinch of salt and cook the spaghetti until al dente according to package instructions. Drain and set aside.

Add the cooked spaghetti to the sauce in the skillet, tossing well to coat every strand with the rich, flavorful sauce. Garnish with parsley before serving!