Start by bringing a large pot of salted water to a rapid boil over high heat. Add the pasta and cook until al dente, about 8-10 minutes. Reserve ½ cup of pasta water, then drain the pasta and set it aside.

Slice the chicken breasts lengthwise and season with garlic powder, salt, and pepper. Heat olive oil and butter in a large skillet over medium-high heat. Sauté the chicken for 5-7 minutes until golden and cooked through. Remove and let it rest.

In the same skillet, sprinkle in flour to make a roux. Stir continuously for about 1 minute to cook the flour slightly.

Gradually pour in chicken broth while whisking, then add heavy cream and pesto. If using, add a splash of lemon juice. Simmer for 3-5 minutes until it thickens slightly.

Stir in sun-dried tomatoes and fresh spinach. Cook for an additional 2-3 minutes until the spinach wilts.

Add the drained pasta to the skillet and toss gently, gradually adding reserved pasta water until the desired consistency is reached.

Slice the cooked chicken into bite-sized pieces and mix with the pasta. Serve hot, garnished with Parmesan cheese if desired.