Step 1: Cook the Pasta
Bring a large pot of generously salted water to a rolling boil. Add the pasta and cook according to package directions until al dente. Reserve 1 cup of the starchy pasta water before draining. This liquid gold is essential for creating a silky, emulsified sauce. Drain the pasta and set it aside.

Step 2: Sear the Chicken
While the pasta cooks, pat the chicken cubes completely dry with paper towels. Season generously with salt, pepper, and Italian seasoning or paprika. In a large, heavy-bottomed skillet (cast iron or stainless steel are ideal), heat the olive oil and 1 tablespoon of the butter over medium-high heat. Once hot, add the chicken in a single layer, ensuring not to overcrowd the pan (cook in batches if necessary). Cook for 5-7 minutes, turning occasionally, until the chicken is cooked through and has a beautiful golden-brown sear on all sides. Remove the chicken from the skillet and set it aside on a plate.

Step 3: Build the Garlic Butter Sauce
Reduce the heat to medium-low. Add the remaining 5 tablespoons of butter to the skillet. Once melted, add the minced garlic. Sauté for about 1-2 minutes, stirring constantly, until the garlic is incredibly fragrant and just beginning to turn golden. Do not let it brown, as it will become bitter.

Step 4: Deglaze and Create the Sauce Base
Pour the chicken broth or white wine into the skillet to deglaze. Use a wooden spoon to scrape up all the delicious browned bits (fond) from the bottom of the pan. Let it simmer for 1-2 minutes until reduced by half.

Step 5: Emulsify the Sauce
If using, stir in the heavy cream. Then, gradually whisk in about ½ cup of the reserved starchy pasta water. The starch will help thicken the sauce and help it cling to the pasta. Bring the sauce to a gentle simmer.

Step 6: Combine Everything in the Skillet
Reduce the heat to low. Add the cooked, drained pasta and the seared chicken (with any accumulated juices) back into the skillet. Toss everything together to coat in the sauce. Gradually sprinkle in the grated Parmesan cheese, tossing constantly until it melts and creates a creamy, cohesive sauce. If the sauce is too thick, add more reserved pasta water, a tablespoon at a time, until it reaches your desired consistency.

Step 7: Finish with Freshness
Remove the skillet from the heat. Stir in the fresh lemon juice, chopped parsley, and optional red pepper flakes. Taste and adjust seasoning with salt and pepper.

Step 8: Serve Immediately
Divide the pasta and chicken among bowls or plates. Garnish with additional parsley, a sprinkle of Parmesan cheese, and a lemon wedge on the side for an extra bright squeeze. Serve immediately while hot and steaming.