Tip the peanuts into a dry wok or deep frying pan. Toast over a medium heat for 3-4 mins till golden. Tip out into a clean tea towel. Let them cool for a few mins, then give a rub to remove the skins.
Tip 1 tsp peppercorns into a mortar and pestle. Roughly crush them. No mortar and pestle? Put them in a small bowl and use the bottom of a jam jar or the end of a rolling pin to crush them. Add the peanuts and crush them with the peppercorns.
Add 1 tsp dried chilli flakes to the peppercorns (or more, if you prefer a spicier meal). Stir in 2 tbsp red wine vinegar, the tamari, tahini and 1 tbsp oil. Stir well to make a thick sauce. Set aside.
Trim the ends off the leek. Slice a cross into the top of it, cutting down about 3cm. Rinse under cold water to wash out any grit. Finely slice it. Halve, quarter or slice the mushrooms, depending on how big they are. Finely slice the cavolo nero leaves, discarding the dry ends.
Warm a wok or deep frying pan over a high heat for 1 min. Add ½ tbsp oil and the leek and mushrooms. Stir fry for 4-5 mins till the veg are soft and juicy looking. Scoop into a bowl or onto a plate.
While the veg cook, put the noodles in a large heatproof bowl or dish. Poor over enough boiling water to cover them. Leave them for 4 mins to soften, then drain well.
Add the lamb mince. Stir fry for 10-12 mins till browned all over, using a wooden spoon to break up any lumps and draining off any excess liquid.
When the mince is browned, add the tahini sauce. Stir fry for 2-3 mins to mix everything together and warm it through.
Tip the veg back into the pan. Add the noodles and the cavolo nero. Stir fry for 3-4 mins till the cavolo nero is lightly cooked and everything is well mixed. Divide the lamb noodles between two warm bowls and serve straight away.