Start by boiling a large pot of salted water. Once boiling, add the pasta and cook according to package instructions until al dente. Reserve 1 cup of pasta cooking water, then drain the pasta in a colander.
While the pasta is cooking, heat olive oil in a skillet over medium heat. Add the diced chicken and cook for about 5-7 minutes, or until the chicken is golden brown and cooked through. Remove the chicken from the skillet and set aside.
In the same skillet, add the chopped onion and cook for about 3-4 minutes until translucent. Add the minced garlic and cook for an additional 1 minute until fragrant.
Pour in the crushed tomatoes, followed by the butter. Stir until the butter melts and the sauce is combined. Add the dried basil, salt, and black pepper, stirring well.
Return the cooked chicken to the skillet and mix it with the tomato butter sauce. Gently toss in the cooked pasta, adding reserved pasta water a little at a time until the desired consistency is reached.
Finally, remove from heat and stir in the grated Parmesan cheese until well incorporated. Serve hot, garnished with fresh basil leaves if desired.