Bring a large pot of salted water to a boil. While the water heats, melt the butter with the chile crisp in a large skillet over low heat.
STEP 2
Whisk in the cream and keep warm over low heat (it should steam, not bubble).
STEP 3
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.
STEP 4
Add the spinach and turn with tongs until the noodles are well coated.
STEP 5
Add the Parmesan and toss until the noodles are slicked with a creamy sauce, adding spoonfuls of pasta water if needed. Divide among serving dishes and top with more Parmesan and chile crisp, if desired. Serve immediately.