Remove shell of the prawns, rub in coarse salt and rinse a few times. Note that once prawns are cleaned will weigh about 700gram. Squeeze excess water and marinate the prawns with chilli flakes, birds eye chilli, garlic, zest and juice of 1 lemon and salt. Refrigerate for 30 minutes
Boil pasta in salted water as per instructions on the packet. Cook until al la dente, drain the water. Reserve some of the pasta water to add to the final dish. Return the pasta to the pot to keep warm
Heat one tablespoon butter, with a teaspoon of oil, in a pan and flash fry half the prawns in 2 batches, 30 seconds on each side. Add another tablespoon of butter and fry remaining prawns. Transfer to a bowl and set aside
Melt 2 tablespoon of butter to the same pan. Add the flour and cook for a minute.
Add cream and simmer until sauce is thick, about another minute. Add the pasta water. Add more salt and some pepper. Add prawns to the sauce and let it heat through. Drizzle more lemon juice into the pasta.
Divide pasta into pasta bowls and add the prawn sauce on top. Garnish with parsley and add some parmesan if you prefer. You can also mix the sauce and pasta together which is recommended if you want all that saucy goodness.