Tip the peanuts into a dry wok or deep frying pan. Toast over a medium heat for 3-4 mins till golden. Tip out onto a board, roughly chop them and pop in a medium bowl.
Tip 1 tsp Szechuan peppercorns into a pestle and mortar and roughly crush them. No pestle and mortar? Put them in a small, sturdy bowl and use the bottom of a jam jar or the end of a rolling pin to crush them. Add the crushed peppercorns to the peanuts.
Halve the chilli and finely chop it, discarding the seeds and white pith for less heat. Add to the peanuts and peppercorns with 2 tbsp balsamic vinegar, the tamari, tahini and 1 tbsp oil. Stir well to make a thick sauce. Set aside.
Warm a wok or deep frying pan over a high heat for 1 min. Add ½ tbsp oil and the lamb mince. Stir fry for 10 mins till well browned all over, using a wooden spoon to break up any lumps.
While the lamb fries, peel and finely slice the onion. Halve, quarter or slice the mushrooms, depending on how big they are. Finely slice the cavolo nero leaves, discarding the dry ends.
Drain any excess liquid off the lamb, then scoop the browned mince onto a plate. Add ½ tbsp more oil to the wok with the onion and mushrooms. Stir fry for 4-5 mins till the veg are soft and juicy.
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 mince back into the wok. Pour in the Szechuan peppercorn sauce. Stir fry for 2-3 mins to mix everything together and warm it through.
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.