Boil a large pan of salted water. Tip in the pasta, then cook for about 7 mins. Add the peas, then cook for 2-3 mins more until both are cooked through.
Drain in a colander, reserving a little cooking water, then tip back into the pan with the crab meat and crème fraîche. Stir well with most of the remaining ingredients, adding a little of the pasta cooking water if the mixture seems a little dry.
Serve sprinkled with a little extra chopped chilli, parsley and lemon zest.