Cook the pasta in boiling salted water for about 10 minutes, then drain, reserving some of the cooking water.
Meanwhile, heat the oil in a frying pan over a medium heat. Finely chop the garlic, spring onions and chilli and cook them in the oil for a few minutes, then add the lemon zest and juice and mix in the brown crab meat.
Add the pasta and enough of the reserved cooking water to loosen the mixture - about 3 tablespoons - and then mix in the white crab meat.
Add the chopped parsley and mix through the pasta until it is evenly distributed.
Divide between pasta bowls, top with the cooked prawns, and serve with an extra drizzle of oil and a green salad.