Pour the sunflower oil into a measuring jug—1 cup. Add 1 tablespoon of that oil to a big skillet set on a high heat. As soon as the oil starts smoking, stir in the onions, palm sugar, and salt and drop the heat to medium..
Stir fry the onions on that medium heat for about 4 minutes. You want the onions to pick up a dark golden color—but not blacken—as they crisp and caramelize in the sugary, sizzling oil.
Take special care not to let the onions burn—that will turn them unpleasantly bitter and spoil your relish. The key here is to color and crisp the onions but not to let them become overly charred. And bear in mind that the onions are going to fry for a couple more minutes when they’re joined by the chilies and garlic.
As soon as the onions have turned to a deep gold, add the chilies and garlic. Continue stir frying the mix for another two minutes on medium-high, until the garlic turns a pale gold and the chilies pick up a little darkening char. Good. Now turn the whole lot into a bowl and set it aside.
Return the skillet to a medium-high heat and add another tablespoon of oil from your measuring jug. Let the oil heat for a minute or so, add the chopped peanuts and stir fry them for 2 minutes until they begin to darken a little. Now add 4 tablespoons water and the miso paste. Give the lot a good stir so that the miso completely dissolves into the bubbling mix.
Keep the heat on medium-high and stir in the crisped onion, garlic, chillies, and the remaining oil from your measuring jug. Stir well so that all the ingredients are combined. Nearly done.
When the relish comes back to a lively bubble, turn off the heat and let the relish cool. Once that happens, pour it into a bowl so it’s ready for serving.