Heat the oil and butter n a very large skillet over medium heat.
Add the onions and cook, stirring often, for 3 minutes.
Add the mushrooms and crushed red pepper flakes then cook, stirring occasionally, for 4-5 minutes.
Add the minced garlic and cook, stirring constantly, for 1 minute.
Add the chicken broth and scrape up all bits from the bottom of the pan.
Add the jar of marinara sauce and the heavy cream; mix until well combined. Taste then season with sea salt and freshly cracked pepper, to taste.
Nestle the tortellini in the sauce so they are submerged.
Cover with a lid and cook for 9-11 minutes, or until the tortellini are tender and cooked through.
Remove the lid and add the baby spinach; stir until combined.
Serve immediately with freshly chopped basil and shaved parmesan on top. Enjoy.