Sear the Salmon:
Pat the salmon fillets dry and season with salt and pepper. Heat butter and olive oil in a large skillet over medium-high heat.
Sear the salmon, skin side down, for 4–5 minutes per side until golden and cooked through. Remove and set aside.
Sauté the Vegetables:
In the same skillet, melt a little more butter if needed. Add sliced mushrooms and cook until soft and lightly browned.
Stir in the minced garlic and cook for 30 seconds, until fragrant.
Make the Cream Sauce:
Lower heat to medium. Pour in the heavy cream, stir gently, and add Parmesan cheese, chili flakes, salt, and pepper.
Simmer for 2–3 minutes until the sauce slightly thickens.
Add Spinach and Return the Salmon:
Stir in the spinach until wilted. Gently return the salmon fillets to the skillet, spooning sauce over each piece.
Finish and Serve:
Squeeze lemon juice over the top and garnish with chopped parsley.
Serve hot with rice, pasta, mashed potatoes, or crusty bread.