Warm olive oil in a large skillet over medium heat until it shimmers. Add chicken breast pieces, ensuring they are in a single layer. Cook for about 5 minutes, turning occasionally, until they are evenly browned on all sides. Remove the chicken from the skillet and set aside on a plate.

In the same skillet over medium heat, add diced onion and cook, stirring occasionally, until it becomes soft and translucent, about 3 minutes. Next, add minced garlic and continue cooking, stirring constantly, until the garlic releases its aroma and turns golden, approximately 1 minute.

Place the chicken back into the skillet over medium heat. Evenly sprinkle dried oregano over the chicken, stirring gently to ensure the spices coat each piece. Cook for about 5 minutes, allowing the chicken to absorb the flavors and become golden brown, stirring occasionally to prevent sticking or burning.

Add the diced tomatoes and chicken broth to the skillet, ensuring they are evenly distributed. Stir thoroughly, using a wooden spoon to scrape up any browned bits stuck to the bottom. This will enhance the depth of flavor. Bring the mixture to a gentle simmer over medium heat, allowing the ingredients to meld together for about 5 minutes.

Add the uncooked pasta to the skillet, ensuring it is fully submerged in the liquid. Increase the heat to medium-high until the mixture reaches a rolling boil. Once boiling, reduce the heat to low, cover the skillet with a lid, and let it simmer gently for 12-15 minutes, stirring occasionally to prevent sticking.

Allow the mixture to simmer gently over medium heat for 10-12 minutes, stirring occasionally to prevent sticking. The pasta should reach an al dente texture, absorbing most of the liquid. Look for a slight firmness when bitten, and ensure the sauce has thickened slightly, coating the pasta evenly.

Gently fold in the fresh spinach, ensuring it is evenly distributed throughout the pasta. Allow the spinach to wilt from the residual heat, stirring occasionally. This process should take approximately 2 minutes, during which the spinach will become tender and vibrant green, blending seamlessly with the pasta.

Take the skillet off the heat and immediately add the grated Parmesan cheese. Stir continuously for about two minutes until the cheese is fully melted and smoothly integrated into the dish. The mixture should appear creamy and the cheese should no longer be visible as separate shreds.

Sprinkle salt and pepper over the dish, stirring gently to combine. Taste the mixture and adjust the seasoning as needed, ensuring a balanced flavor profile. Continue cooking over medium heat, allowing the ingredients to meld together for an additional 5 minutes, until the aroma is inviting and the dish is well-seasoned.

Just before serving, sprinkle chopped fresh basil over the dish. This will enhance the aroma and provide a vibrant green color, complementing the other ingredients. The basil should be added at the last moment to maintain its freshness and prevent wilting from the heat of the dish.