Heat a large skillet over medium-high heat. Add the olive oil and butter.
Once the butter is melted, add the shrimp to the skillet in a single layer. Cook for 1-2 minutes on each side, or until the shrimp are pink and opaque. Remove the shrimp from the skillet and set aside.
Make the Sauce:
In the same skillet, add the additional 2 tablespoons of butter.
Add the minced garlic and chopped onion. Sauté for 2-3 minutes, or until the onion is translucent.
Stir in the sun-dried tomatoes and cook for another minute.
Pour in the chicken broth to deglaze the pan, scraping up any browned bits from the bottom of the skillet.
Add the heavy cream, Parmesan cheese, Italian seasoning, and red pepper flakes (if using). Stir to combine.
Season the sauce with salt and pepper to taste. Let it simmer for 5-7 minutes, or until it starts to thicken.
Combine Shrimp and Sauce:
Return the cooked shrimp to the skillet. Stir to coat the shrimp in the sauce.
Add the baby spinach and fresh basil. Cook for 2-3 minutes, or until the spinach is wilted.
Serve:
Serve the Creamy Tuscan Shrimp over cooked pasta, rice, or with crusty bread to soak up the delicious sauce.
Garnish with additional Parmesan cheese and fresh basil, if desired.