The sauce is four things in balance: fat, salt, heat and sour. Get those right and the specific ingredients matter much less than recipes pretend.
Make the sauce in the pan before the noodles go anywhere near it. Peanut butter added to hot noodles seizes into lumps that never come out.
- Coconut milk into the pan over low heat with the garlic, ginger and chilli. Warm it, do not boil it.
- Peanut butter in off the heat, stirred until it disappears. If it is claggy, a splash more coconut milk.
- Soy sauce and sugar in, back on a low heat for two minutes to loosen.
- Noodles cooked separately, drained, and tipped in with a splash of their water. Toss hard.
- Lemon juice at the very end, off the heat.
Taste before the lemon and after it. The difference is the whole lesson in this dish: before, it is rich and flat; after, it is a sauce.
Serves 3.