Follow these steps carefully for perfect Mushroom Spinach Alfredo Pasta every time:

1. Cook the Pasta: Bring a large pot of water to a rolling boil. Add a generous amount of salt (it should taste like the sea – this seasons the pasta from within). Add the fettuccine and cook according to package directions until al dente (typically 8-10 minutes). Crucially, before draining, reserve about 1-2 cups of the starchy pasta water. Drain the pasta but do not rinse it. You can toss it with a tiny drizzle of olive oil to prevent sticking if it sits for a minute or two, but it’s best to time it so the pasta is ready just as the sauce finishes.
2. Sauté the Mushrooms: While the pasta is cooking, melt 2 tablespoons of the butter in a large, deep skillet or Dutch oven over medium-high heat. Once the butter is melted and shimmering, add the sliced mushrooms. Spread them in a single layer as much as possible (cook in batches if necessary to avoid overcrowding the pan). Cook, stirring occasionally, for about 5-7 minutes, until they release their liquid, it evaporates, and the mushrooms become nicely browned and slightly caramelized. This browning step develops their deep, savory flavor.
3. Add Aromatics: Push the mushrooms to one side of the skillet. Add the remaining 6 tablespoons of butter to the empty side. Once melted, add the minced garlic and sauté for about 30-60 seconds until fragrant. Be careful not to burn the garlic, which can make it bitter. Stir the garlic into the mushrooms.
4. Wilt the Spinach: Add the fresh spinach to the skillet with the mushrooms and garlic. It might seem like a huge amount, but it will wilt quickly. Gently toss the spinach with tongs as it cooks down, which should only take 1-2 minutes. Season lightly with a pinch of salt and pepper.
5. Start the Alfredo Sauce: Reduce the heat to medium-low. Pour the heavy cream into the skillet. Let it heat gently for a minute or two, stirring occasionally. Do not let it come to a rapid boil.
6. Incorporate Parmesan: Gradually add the freshly grated Parmesan cheese, about 1/2 cup at a time, stirring constantly until each addition is melted and the sauce is smooth before adding the next. This slow addition and constant stirring over low heat is key to preventing the cheese from clumping. Continue stirring until all the cheese is incorporated and the sauce is velvety smooth.
7. Season the Sauce: Stir in the remaining salt (start with about 1 teaspoon, taste, and adjust), freshly cracked black pepper, and the optional pinch of freshly grated nutmeg. Taste the sauce and adjust seasoning as needed. Remember the pasta water is salty, so don’t over-salt at this stage.
8. Combine Pasta and Sauce: Add the drained fettuccine directly into the skillet with the Alfredo sauce, mushrooms, and spinach. Use tongs to toss everything together thoroughly, ensuring every strand of pasta is coated in the luscious sauce.
9. Adjust Consistency (If Needed): If the sauce seems too thick, add a splash (a tablespoon or two at a time) of the reserved hot pasta water. The starchy water will help thin the sauce slightly while also helping it emulsify and cling beautifully to the noodles. Toss well after each addition until you reach your desired consistency. The sauce will continue to thicken slightly as it cools.
10. Serve Immediately: Dish the Mushroom Spinach Alfredo Pasta into warm bowls. Garnish generously with extra freshly grated Parmesan cheese and perhaps a sprinkle of fresh parsley or red pepper flakes if desired. Enjoy immediately for the best texture and flavor.
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