Cook the pork steaks: Heat the olive oil or butter in a large skillet over medium-high heat. Season the pork steaks with salt and pepper. Sear the pork steaks for 4-5 minutes on each side, until browned and cooked through. Remove the pork from the skillet and set aside.

Sauté the onions and garlic: In the same skillet, reduce the heat to medium and add the chopped onions and garlic. Sauté for 3-4 minutes until softened and fragrant.

Prepare the mustard sauce: Stir in the chicken or beef broth, scraping up any browned bits from the bottom of the skillet. Add the Dijon mustard, whole-grain mustard (if using), and fresh thyme. Stir to combine and let the sauce simmer for 3-4 minutes.

Finish with cream: Lower the heat and stir in the heavy cream. Let the sauce simmer for 5 minutes until it thickens slightly. Season with salt and pepper to taste.

Serve: Return the pork steaks to the skillet, spooning the mustard sauce over them. Let the pork steaks warm through for 2-3 minutes. Garnish with fresh parsley and serve hot.