In a large pot, bring salted water to a boil and cook the penne pasta according to the package instructions until al dente. Drain and set aside.
In a large skillet, heat the olive oil over medium heat. Add the diced chicken breast, seasoning with salt, pepper, and Italian seasoning. Cook until browned and cooked through, about 6-7 minutes. Remove the chicken from the skillet and set aside.
In the same skillet, add the chopped onion and minced garlic. Sauté until the onion is translucent, about 3-4 minutes.
Lower the heat and pour in the heavy cream, stirring to combine. Gradually add the shredded mozzarella and Parmesan cheese, stirring until melted and smooth.
Add the cooked pasta, sautéed chicken, and halved cherry tomatoes to the cheese sauce. Toss everything together until well coated.
Let the mixture cook for an additional 2-3 minutes on low heat so everything warms through, adding more cream if the sauce needs thinning. Adjust salt and pepper to taste.
Serve immediately, garnished with fresh basil leaves.
Notes
Adjust the seasoning to taste and add more cream if needed.