1. Prepare and Sear the Chicken:
Pat the chicken completely dry with paper towels; this is essential for getting a good sear. Season both sides generously with salt, black pepper, and garlic powder. Heat the olive oil in a large, heavy-bottomed skillet or Dutch oven over medium-high heat. Once the oil is shimmering, carefully place the chicken in the skillet in a single layer (work in batches if necessary to avoid overcrowding). Cook for 5-7 minutes per side, until golden brown and cooked through. Remove the chicken from the skillet and set it aside on a plate.

2. Sauté the Aromatics:
Reduce the heat to medium. Add the butter and the reserved tablespoon of oil from the sun-dried tomato jar to the skillet. Add the finely chopped onion and cook for 3-4 minutes until softened and translucent. Add the minced garlic and chopped sun-dried tomatoes. Sauté for another minute until the garlic is fragrant, being careful not to let it burn.

3. Deglaze the Pan and Build the Sauce:
Pour in the dry white wine (or chicken broth) to deglaze the pan. Use a wooden spoon or spatula to scrape up all the flavorful browned bits from the bottom of the skillet. Let the wine simmer and reduce by about half, which should take about 2-3 minutes.

4. Create the Creamy Sauce:
Reduce the heat to medium-low. Whisk in the heavy cream and the ½ cup of chicken broth. Bring the mixture to a gentle simmer (do not let it come to a rolling boil). Stir in the freshly grated Parmesan cheese until it has melted smoothly into the sauce. Season the sauce with the dried oregano and optional red pepper flakes.

5. Bring It All Together:
Return the seared chicken and any juices from the plate back into the skillet, nestling it into the creamy sauce. Let it simmer gently in the sauce for 3-5 minutes to allow the flavors to meld and the chicken to heat through.

6. Wilt the Spinach:
Add the fresh spinach to the skillet in large handfuls, stirring it into the sauce until it wilts down. This will only take 1-2 minutes.

7. Garnish and Serve:
Taste the sauce and adjust seasoning if necessary (it may need another pinch of salt or pepper). Garnish generously with fresh chopped basil or parsley. Serve immediately.