Bring a large pot of salted water to a boil and cook the pasta until al dente, then drain and set aside to prevent soft and soggy noodles.
Chop chicken into bite-sized pieces and toss in a bowl with olive oil, garlic, Italian seasoning, salt, and pepper so each piece is well coated before cooking.
Heat a large frying pan over medium-high, add the chicken in a single layer, and leave undisturbed for 2 to 3 minutes until golden before stirring.
Stir in drained, chopped sun-dried tomatoes and cook with the chicken for about 5 to 7 minutes until the chicken is cooked through.
In a small bowl, whisk together milk and gluten-free flour until smooth, making sure there are no lumps.
Pour the milk mixture over the chicken, bring it to a gentle bubble, and let it cook for 3 to 4 minutes until it thickens into a creamy consistency.
Reduce heat, add the baby spinach and stir until wilted, then turn off the heat, toss in the drained pasta and Parmesan, and stir until everything is well coated and creamy.