To make the pasta, sift the flours and a pinch of salt into a mixing bowl. Make a well in the centre, pour in 175 ml (6 fl oz) of water and stir to make a firm but not sticky dough. Add another tablespoon of water if the mixture is too dry, or of flour if it is too wet.
Knead the dough for 3-4 minutes until it becomes elastic, then cover loosely with cling film and set aside for at least 30 minutes to rest.
Meanwhile, to make the filling, put the crabmeat in a sieve and leave it to drain. Then place it in a bowl with the egg whites, basil, coriander, chilli, garlic and ginger and mix well. Season with black pepper to taste and set aside.
Cut the pasta dough into eight equal pieces, then roll each piece into a long strip. Set the pasta machine to its widest setting and roll one strip of dough through it. Fold the dough in half, lightly dust it with flour to prevent sticking and roll it through the machine again. Fold, dust and roll the dough through the machine once more, then set it aside. Repeat the process with the remaining strips.
Set the machine to the next setting and roll each strip of dough through once, then lower the setting and roll each piece of dough through again. Continue lowering the settings and rolling the dough through until you get to the fifth or sixth setting – the dough should be very thin but not transparent.
Put a large pan of water on to boil.
Use a serrated 4-5 cm (1½-2 in) biscuit cutter to stamp out rounds of dough. Place 1-2 heaped teaspoons of filling in the centre of half the rounds, dampen the edges with water and lay the remaining rounds on top. Press the edges firmly together to enclose the filling and to thin the double layer of dough slightly. Alternatively, cut and fill the ravioli with ravioli trays, following the manufacturer's instructions.
Working in batches, lower the ravioli into the boiling water and cook for 3 minutes, then drain them in a colander and keep them warm. Arrange the ravioli on plates and sprinkle them lightly with a few drops of sesame oil and fresh basil. Serve with steamed vegetables such as ribbons of carrot and leek.
Variation: if you do not have a pasta machine, use won ton wrappers to enclose the filling, and steam them for 5 minutes. If you cannot find semolina flour or Italian pasta flour, use strong plain white flour.