Bring a large pot of salted water to a boil.
While the water heats, in a very large skillet or Dutch oven, over low heat, melt the butter with the chile crisp.
Whisk in the cream; keep warm over low heat; it should steam, not bubble.
Cook the fettuccine until al dente according to the package directions.
Use tongs to transfer the noodles to the cream mixture, reserving the pasta water.
Add the spinach and turn with tongs until the noodles are well coated.
Add the Parmesan and toss, still over low heat, until the noodles are slicked with a creamy sauce, adding a spoonful or two of pasta water, if needed to loosen the sauce.
Divide among serving dishes and top with Parmesan and more chile crisp, if desired.
Should be served immediately.
This was absolutely incredible. Will be making over and over.