01 - Bring a large pot of salted water to a boil. Cook fettuccine or linguine according to package directions until al dente. Reserve 1/2 cup of pasta water before draining. Set pasta aside.
02 - Pat the chicken and shrimp dry with paper towels. Season both lightly with salt and freshly ground black pepper on all sides.
03 - Heat 1 tbsp olive oil in a large skillet over medium-high heat. Add the chicken pieces in a single layer and sauté until golden brown and cooked through, approximately 5-6 minutes. Transfer to a plate and tent loosely with foil.
04 - Add the remaining 1 tbsp olive oil to the same skillet. Sear the shrimp for 2-3 minutes, flipping once, until they turn pink and become opaque throughout. Remove and set aside with the chicken.
05 - Reduce heat to medium. Melt the butter in the skillet and sauté the minced garlic for about 1 minute, stirring constantly, until fragrant and lightly golden.
06 - Pour in the heavy cream and bring to a gentle simmer. Stir in the Parmesan cheese, lemon zest, lemon juice, red pepper flakes (if using), salt, and pepper. Simmer for 2-3 minutes, stirring frequently, until the sauce coats the back of a spoon.
07 - Return the chicken and shrimp to the skillet. Add the drained pasta and toss everything together, incorporating reserved pasta water a splash at a time until the sauce reaches your desired consistency.
08 - Fold in the chopped parsley and taste the dish. Adjust salt and pepper as needed to balance the lemon and garlic flavors.
09 - Divide among warmed plates or bowls. Garnish generously with freshly grated Parmesan and serve with lemon wedges on the side.