I was rather worried someone might ask, and Lavinia did. The recipe? I made it up and have no idea how they're going to taste, you see... I looked at three recipes online and decided to wing it, using elements of each.
For four small mason jars there were:
five bunches of small onions
1/2 cup sherry vinegar
2 cups water
1 Tbsp salt
2 Tbsp brown sugar
4 Tbsp mustard seeds
1 fiery chile, sliced into rings
I cleaned the onions and soaked them overnight in cold water with about 5 Tbsp of salt added. Next day I brought the water and 1/2 cup vinegar to a boil, added the mustard seeds, salt, and sugar. When cooler I poured this over the onions which I had drained and packed into the sterilized mason jars. Then put them into the fridge and will taste in a couple weeks. Other recipes use a lot more vinegar...so...we'll see?