In a large pot of salted boiling water, cook the tortellini according to package instructions until al dente. Drain and set aside.
In a large skillet, heat the olive oil over medium heat. Add the minced garlic and sauté for about 1 minute until fragrant.
Pour in the heavy cream and bring to a gentle simmer. Add the chopped spinach and cook for 2-3 minutes until the spinach is wilted.
Stir in the Italian seasoning, salt, pepper, and red pepper flakes if using. Allow the mixture to simmer for another 2 minutes, stirring occasionally.
Add the cooked tortellini into the skillet, tossing gently to coat the pasta in the creamy sauce. Gradually mix in the grated Parmesan cheese until melted and well combined.
If the sauce is too thick, you can add a splash of pasta water to loosen it. Taste and adjust seasoning as needed.
Transfer the creamy tortellini to serving plates or a large serving dish. Garnish with fresh basil leaves and additional Parmesan if desired.