Peel and chop the potatoes into 2cm chunks. Bring a pan of salted water to the boil. Once boiling, drop the potatoes in and cook for 10-15 mins until fork tender. Drain the potatoes through a fine mesh sieve, reserving 100ml of the cooking water.

Place the sieve with potatoes on top of a bowl. Working quickly, push the potatoes through to create a fine mash (or use a ricer for quicker results). Mix through the potato starch and three-quarters of the hot potato water, until a smooth dough forms. If it looks a bit dry, add more of the potato water until smooth.

Bring another pan of water to the boil. Divide the dough into 16 even pieces, then roll each one into a long, 1cm-thick log. Cover the noodles with wet kitchen paper.

Once the water comes to a boil, drop the noodles in and cook for 5 mins. Place the noodles into a bowl of ice water, reserving 400ml of the cooking liquid.

Coarsely grind the peppercorns, then add them to a dry frying pan set over a medium heat and toast until fragrant. Add 200ml reserved noodle water and let reduce by half. Add the noodles with the cold butter and toss until emulsified. Remove from the heat and toss the parmesan in little by little (leaving some for garnish) until a creamy sauce forms. Add a splash of noodle water to loosen, if needed. Taste and season with salt before serving.

Toss the cooked noodles through the sauce, then share between bowls and sprinkle with the remaining Parmesan.