Cook the fettuccine to al dente in a large pot of well-salted boiling water according to the package instructions; drain, reserving ½ cup of pasta cooking water.
Meanwhile, make the sauce by melting the butter with the chile crisp in a very large skillet over medium-low heat.
Whisk in the cream and keep warm over low heat. (It should simmer, not bubble.) Season with sea salt and freshly cracked black pepper to taste.
Add the drained noodles to the cream mixture, stirring to coat evenly.
Add the spinach and turn with tongs until the noodles are well coated.
Finish the dish by adding the Parmesan and tossing, still over low heat, until the noodles are coated with the creamy sauce, adding a spoonful or two of pasta water as needed to loosen the sauce.
Serve by dividing among serving dishes and top with Parmesan and more chile crisp. Serve immediately. Enjoy.