Season salmon on both sides with salt, pepper and dried basil.
Heat oil and 1 tbsp of unsalted butter in large skillet over medium-high heat. Add salmon and thyme sprigs. Cook for 3 minutes on both sides. Remove from skillet, and set aside.
Reduce heat to medium. Give skillet time to cool down, and melt 3 tbsp of butter in skillet. Add garlic and cook until fragrant, about 2 minutes.
Stir in heavy cream, sherry wine and lemon juice. Season with a little salt and pepper. Simmer until sauce starts to thicken, about 7 minutes.
Return salmon to skillet, and add lemon slices. Simmer for additional 5 minutes. Serve warm.