In a small bowl combine the kosher salt, pepper, onion powder, and paprika. Season chicken on both sides liberally.
Add the sun-dried tomato oil to a large skillet and heat over medium heat for 2-3 min. Add the chicken; you should hear a sizzle, meaning the oil is hot enough. Cook for 5 min on first side; then flip and cook 5 more minutes. It should be cooked through. Put the chicken on a clean plate and set aside.
Reduce heat to low-medium heat. Add the garlic to the pan and saute for 30 seconds. Add chicken stock and scrape up any brown bits stuck to bottom of pan.
Add in the sun-dried tomatoes and Dijon mustard, mix and allow to cook a couple minutes while stirring.
Add the heavy cream and bring to a gentle simmer, stirring occasionally. Taste and add salt and pepper if necessary.
Add in the spinach leaves, stir and allow to wilt.
Add in the parmesan cheese. Stir and bring to a simmer for 1 minute.
Add the chicken back into the pan (including any juices); top with parsley and serve over pasta.