Heat a large skillet over medium-high heat. melt the butter and add in the garlic. Fry until fragrant (about 1 minute). Add in the shrimp and fry two minutes on each side, until just cooked through and pink. Transfer to a bowl; set aside.
Fry the onion in butter remaining in skillet. Add the sun dried tomatoes and fry for 1-2 minutes to release their flavors.
Reduce heat to low-medium heat, add the half and half 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, and add the parmesan cheese. Allow sauce to simmer for a minute until cheese melts through the sauce. Add the cornstarch/water mixture and continue to simmer while stirring until the sauce thickens.
Add the shrimp back into the pan; sprinkle with herbs and parsley, and stir through.