Pat the salmon fillet completely dry with paper towels and season both sides with half of the sea salt and black pepper.
Heat the ghee in a large stainless steel or cast iron skillet over medium-high heat until it begins to shimmer.
Carefully place the salmon in the pan skin-side down and press gently with a spatula for 10 seconds to ensure even contact.
Sear the salmon for 4 to 5 minutes without moving it until the skin is golden and crispy, then flip and cook for 2 more minutes.
Remove the salmon from the pan and set it aside on a warm plate to rest.
In the same skillet, add the sliced mushrooms and sauté for 3 to 4 minutes until they have released their moisture and turned brown.
Add the minced garlic and baby spinach to the mushrooms, stirring constantly until the spinach is fully wilted.
Reduce the heat to low, stir in the coconut milk and the remaining salt and pepper, and simmer for 1 minute until the sauce is thick and creamy.
Plate the creamed spinach and mushroom mixture first, then top with the pan-seared salmon fillet.