Dust fish lightly with salt and pepper to taste.

Melt ghee in a skillet over medium heat; sauté fish until brown, about 2 to 3 minutes per side; remove from skillet and keep warm.

Pour broth into the skillet, bring to a boil and scrape up all of the browned bits from the bottom of the pan.

Add ginger and cook, stirring frequently, for 2 minutes.

Stir in mustards and shallots; season with salt and pepper and spoon sauce over fish and spinach and serve.