Heat a large skillet over medium-high heat. Melt one tablespoon of butter with the oil. Add in the shrimp and fry for two minutes on each side, until just cooked through and pink. Transfer to a bowl; set aside. Fry the onion in the remaining butter until soft. Add in the garlic and saute until fragrant (about one minute). Pour in the white wine (if using) and reduce to half, while scraping any bits off of the bottom of the pan. Add the sun-dried tomatoes and fry for 2 minutes to release their flavors. Reduce heat to low-medium, add the half and half or heavy cream, and bring to a gentle simmer while stirring occasionally. Season with salt and pepper to your taste. Add in the spinach leaves and allow to wilt in the sauce. Mix in the parmesan cheese. Allow sauce to simmer for a further minute until cheese melts through the sauce. (For a thicker sauce, add the milk/cornstarch mixture to the center of the pan, and continue to simmer while quickly stirring the mixture through until the sauce thickens.) Add the shrimp back into the pan; sprinkle with the herbs and parsley, and stir through. Serve over pasta, rice or steamed veg.