1. Make a mixture of vinegar and sugar, then stir in onions, Sriracha, and celery seeds.
2. Pour the marinade over the chopped stems, using 3 cups liquid for every 1 1/2 cups chopped stems.
3. Throw it in the refrigerator for a few days, and you've got the ultimate refrigerator pickles. Makes about 1 1/2 cups.