1 large bunch of rainbow chard stems cleaned and cut to fit into mason jar, about 3/4 inch from the lip
1/2 cup rice wine vinegar
3/4 cup distilled white vinegar
1/4 cup sugar (or 3 Tbsp maple syrup)
1.5 tsp salt
1.5 Tbsp sriracha or dried pepper flakes
1/4 tsp celery seed divided
1/2 tsp black peppercorns divided
1/2 tsp yellow mustard seeds divided
2 cloves garlic divided
Directions
Add each half of the celery seed, peppercorns, mustard seeds, and garlic to each jar. (If just making one jar, this can all go together.)
Pack chard stems tightly into 2 jars.
Bring vinegars, sugar (or maple syrup), salt, and sriracha (or pepper flakes) to a boil, in a small saucepan until sugar and salt is dissolved. Then pour over chard stems.
Let sit until cool, then put lids on and refrigerate. Wait two days before eating for flavors fully develop. Will last 1 month in refrigerator.