01 - Preheat an outdoor grill or grill pan to medium-high heat.
02 - In a small bowl, combine the olive oil, dried Italian herbs, minced garlic, salt, and pepper. Rub the mixture evenly over both sides of the chicken breasts.
03 - Place the seasoned chicken on the hot grill. Cook for 5 to 6 minutes per side, or until the internal temperature reaches 165°F and juices run clear. Transfer to a cutting board and let rest for 5 minutes before slicing thinly against the grain.
04 - While the chicken grills, bring a large pot of salted water to a boil. Cook the pasta according to package directions until al dente. Reserve ½ cup of the starchy pasta water, then drain the pasta and set aside.
05 - In a large skillet over medium heat, melt the butter. Add the chopped onion and cook for 2 to 3 minutes until softened and translucent. Add the minced garlic and sliced sun-dried tomatoes, and sauté for 1 minute until fragrant.
06 - Pour the chicken broth and heavy cream into the skillet. Bring the mixture to a gentle simmer, stirring occasionally. Gradually whisk in the grated Parmesan cheese until the sauce is smooth and cohesive.
07 - Add the baby spinach to the skillet and cook for about 1 minute, tossing gently, until just wilted. Season with salt and pepper to taste.
08 - Add the drained pasta to the sauce, tossing to coat evenly. If the sauce is too thick, add reserved pasta water a splash at a time until the desired consistency is reached. Fold in the sliced grilled chicken.
09 - Divide among serving plates immediately. Garnish with sliced fresh basil and an extra sprinkle of grated Parmesan before serving.