Pour about 350 ml (12 fl oz) of water into a saucepan and bring to a simmer over medium heat. Pour the water into the bowl of an electric mixer fitted with the whisk attachment, add the combined flours and turn it onto medium speed to incorporate. Add 50 ml (1½ fl oz/2½ tablespoons) of water at a time, mixing continuously. When you are roughly halfway through the process, your dough should look like tiny grey pebbles. At this stage, change the whisk attachment to the dough hook, continue adding the water and work slowly for 7–10 minutes. Please note that doughs can be temperamental with variations in humidity, temperature, air draughts and different batches of flour, so adding the water slowly helps you control these variations. When all the water is incorporated, the dough should nearly stick to your fingers when you touch it. Turn onto a lightly floured cold marble surface or a wooden pasta board.
Cut the dough into 3 portions and cover two of the pieces with a just-damp cloth. Roll out the dough, using flour to dust your rolling pin.
Roll to an even 1–2 mm (1/16 inch) thickness and about the same shape as an A4 (letter) sheet of paper. Gently fold the dough over to make it easier to slice: fold three or four times in one direction. Slice firmly and precisely with a sharp knife: a meat cleaver works best. Fluff the noodles gently with your fingertips coated with flour to separate the initial cut.
Put the noodles in a large saucepan of boiling water and stir gently to make sure the noodles aren’t sticking together. Simmer for approximately 3 minutes until the noodles are al dente. While the noodles are cooking, prepare a bath of ice and water in a large bowl. Place the cooked noodles directly in the ice bath. Once completely cold, place on a clean tea towel (dish towel) and gently dry with another.
Combine the seasoning ingredients in a large bowl, adjusting the chilli oil to taste. Add the noodles, tossing to coat. Place the noodles in serving bowls and serve cold.