Boil the water for the pasta and enough salt (important if you using fresh pasta especially with egg, but you can just start from cold water if using dried pasta but stir actively in the first minute so it doesn't sticking) cook until it's almost al dente

While waiting for pasta, prepare the ingredient for the sauce

When the pasta cook near done, start pouring the oil and set for medium heat and pour the shrimp shells, let it cook for a minute then pick out any shells then add garlic, shallot and shrimps set to medium heat for 1-2 minutes, pour the pasta water and followed by the pasta then add the chili flakes, bring to high heat then let the pasta emulsify into creamy-consistency by adding pasta water little by little

Put and stir the parsley add some lemon juices if desired, set to plate and dress whatever you want it and don't forget to eat :)