Add oil and butter to a large deep skillet over medium heat. Once the skillet is hot, add diced chicken, and onions and cook for about 8-10 minutes until chicken is cooked through and onions are soft.
Next, add remaining ingredients to the skillet and stir to combine. Bring to a low simmer and cook for about 20 minutes or until penne is al dente. When you reach this point, remove pasta from heat, stir, and let sit a couple minutes before serving.
Serve pasta with fresh grated parmesan, red pepper flakes and fresh chopped parsley (optional). Enjoy!
Notes
To store your pasta: Place completely cooled pasta in an airtight storage container in the fridge for up to 2 days.