In a large skillet over medium-high, melt 2 Tbsp butter. Add mushrooms in a single layer and cook undisturbed for 4 minutes, letting them develop a golden sear.
Lower heat to medium. Add remaining butter, sprinkle flour, and whisk into a smooth paste. Cook 1 minute.
Stir in garlic, sun-dried tomatoes, Italian seasoning, and smoked paprika. Sauté 30 seconds until fragrant.
Pour in wine to deglaze (if using), scraping up any brown bits. Whisk in broth, cream, and Parmesan. Simmer 3–5 minutes until sauce thickens.
Remove from heat. Stir in basil and red pepper flakes. Season with salt and pepper.
Serve over pasta, rice, or mashed potatoes.