The day I made this, I had basically nothing in except the listed ingredients, but it turned out quick well, if a touch dry – as peanut butter tends to be.
Boil the pasta as per packet instructions. Finely chop and fry the half onion. Melt the butter and mix int the flour. Add the milk and microwave for 30 seconds, then mix. Add the peanut butter and ginger and mix until you’ve got a paste. Add this to the onion in the frying pan, and mix the sauce with the onions in the pan. Add the soy sauce. Drain the pasta and serve.