Bring a large pot of salted water to a boil. Add rotini and cook according to package directions until al dente. Reserve 1 cup of pasta water, then drain.

While pasta cooks, heat olive oil in a large skillet over medium-high heat. Season chicken pieces with salt, pepper, and Italian seasoning. Cook for 5-7 minutes until golden and cooked through to an internal temperature of 165°F (74°C), stirring occasionally. Remove chicken to a plate.

In the same skillet, reduce heat to medium. Add garlic and sun-dried tomatoes, sauté for 1 minute until fragrant. Pour in chicken broth and heavy cream, bring to a simmer. Stir in Parmesan cheese, red pepper flakes, and a pinch of salt and pepper.

Add spinach to the sauce and cook until wilted, about 1 minute. Return chicken to the skillet. Add drained rotini and toss to coat. If sauce is too thick, add reserved pasta water a splash at a time until desired consistency.

Transfer to a serving bowl, top with fresh basil and extra Parmesan. Serve immediately.