Step 1: Cook the Pasta and Prepare the Chicken
Bring a large pot of water to a rolling boil. Add 1 tablespoon of kosher salt. Cook the pasta according to package directions until al dente. Reserve 1 cup of the starchy pasta water before draining. Drain the pasta but do not rinse it. While the pasta cooks, pat the chicken breasts dry and season both sides generously with salt, black pepper, and garlic powder.

Step 2: Sear the Chicken
In a large skillet (big enough to hold the pasta later), heat 2 tablespoons of butter and the olive oil over medium-high heat. Once the butter is melted and foaming, add the chicken breasts. Sear for 5-7 minutes per side, until golden brown and cooked through (internal temperature of 165°F / 74°C). Transfer the chicken to a clean plate and tent loosely with foil to keep warm.

Step 3: Build the Garlic Base
Reduce the heat to medium-low. Add the remaining 2 tablespoons of butter to the skillet. Once melted, add the minced garlic and red pepper flakes (if using). Cook, stirring constantly, for 1-2 minutes until the garlic is fragrant and just beginning to turn golden. Do not let it brown, or it will become bitter.

Step 4: Deglaze and Create the Sauce Base
Pour in the white wine (or chicken broth) to deglaze the pan, scraping up all the flavorful browned bits from the bottom. Let it simmer for 2-3 minutes until reduced by about half. Stir in the lemon zest, lemon juice, and chicken broth. Bring to a gentle simmer and let it cook for 5-7 minutes, allowing the sauce to reduce and concentrate slightly.

Step 5: Slice the Chicken and Finish the Sauce
While the sauce simmers, slice the rested chicken breasts into ½-inch thick strips or bite-sized pieces. Reduce the heat under the sauce to low. Stir in the grated Parmesan cheese until melted and smooth. Add the tablespoon of cold butter and swirl the pan until it’s fully incorporated, creating a slightly thickened, glossy emulsion.

Step 6: Combine Everything
Add the drained pasta and sliced chicken (with any accumulated juices) to the skillet with the sauce. Using tongs, toss everything together vigorously, adding reserved pasta water a few tablespoons at a time until the sauce reaches a luxurious, clinging consistency that coats every strand of pasta. The starch in the pasta water is key for binding the sauce.

Step 7: Finish with Herbs and Serve
Remove the skillet from the heat. Stir in the chopped fresh parsley. Taste and adjust seasoning with more salt, pepper, or a squeeze of lemon if needed.

Step 8: Plate and Garnish
Divide the pasta and chicken among serving bowls or plates. Garnish with extra fresh parsley, additional grated Parmesan cheese, and serve immediately with lemon wedges on the side for an extra bright burst of flavor.