01 -
Heat 1 cup of heavy cream and 2 tablespoons of butter in a saucepan over medium-low heat until simmering. Simmer for 12-15 minutes, stirring frequently, until reduced to roughly 2/3 cup.
02 -
Remove from heat and stir in the remaining ½ cup heavy cream. Season with sea salt, freshly cracked pepper, and a pinch of grated nutmeg.
03 -
Melt the remaining 1 tablespoon butter in a large skillet over medium heat. Add mushrooms and cook undisturbed for 3 minutes. Toss and continue cooking until golden brown, about 3-4 minutes. Add spinach and minced garlic, stirring constantly for 1 minute. Remove from heat and set aside.
04 -
While the cream reduces, boil fettuccine in salted water following package directions to just before al dente. Drain, reserving ¼ cup of pasta water.
05 -
Return the cream mixture to simmer over medium-high heat, then reduce to low. Add drained pasta and Parmesan cheese. Toss with tongs over low heat until cheese melts, sauce coats pasta, and pasta reaches al dente, about 1-2 minutes.
06 -
Incorporate reserved pasta water if necessary, then stir in the mushroom and spinach mixture. Let thicken for 1-2 minutes off heat, toss again, and serve immediately in warmed bowls. Adjust seasoning with salt and pepper as desired.