Heat a large, deep skillet over medium heat. Add 2 tablespoons of olive oil. Once shimmering, add the mushrooms and season with ¼ teaspoon salt. Toss to coat and cook for 8–10 minutes, stirring occasionally, until browned and their moisture has evaporated. (Note 5: Mushrooms should be golden brown and have a meaty texture.) Remove from the pan and set aside.
12 ounces mushrooms, ¼ teaspoon sea salt
Reduce the heat to medium-low and add the remaining 2 tablespoons of olive oil to the pan. Add the sliced onion and cook for 5–6 minutes, stirring occasionally, until softened and translucent. Stir in the minced garlic and cook for an additional minute, until fragrant.
1 small onion, 2 cloves garlic
Sprinkle the 1 teaspoon dried thyme, 1 teaspoon paprika, and 1 tablespoon all-purpose flour over the onions. Stir well to coat evenly, cooking for 1–2 minutes to eliminate the raw flour taste. Gradually pour in the 2¼ cups chicken or vegetable broth while stirring continuously to prevent lumps. (Note 6: Sauce should be smooth with no visible lumps.)
Stir in the 1 teaspoon Dijon mustard and bring the mixture to a gentle simmer. Cook for 3–4 minutes, allowing the sauce to thicken slightly. Gently fold in the 1 pound shelf-stable or refrigerated gnocchi, ensuring each piece is coated in the sauce. Let cook for 5–7 minutes, stirring occasionally, until the gnocchi are tender and the sauce has thickened. (Note 7: Sauce should coat the back of a spoon, and gnocchi should be soft yet firm to the bite. Test a piece after 5 minutes.)
Return the mushrooms to the skillet, reserving a few for garnish if desired. Stir in the ½ cup sour cream and ¼ cup grated Parmesan cheese until fully incorporated. Simmer gently for 2–3 minutes, allowing the flavors to meld. Taste and adjust seasoning as needed. (Note 8: Sauce should be creamy and well-balanced, with no overpowering flavors.)
Garnish with reserved mushrooms, freshly ground black pepper, minced parsley, and additional Parmesan if desired. Serve immediately and enjoy!