Pack kale stems into a clean 240 ml canning jar. Combine remaining ingredients in a small pot, cover, and bring to a boil over high heat.
Remove brine from heat and pour into the jar of kale stems. You might not use all the brine; reserve any extra for use in salad dressing. But if there are any spices left behind, scoop them out and add them to the kale stems.
Cover the jar and allow to cool to room temperature before refrigerating. Store in the fridge for up to a month.
Notes
Serving suggestions: use on charcuterie plates, in tartar sauce, as a condiment for burgers or curry dishes, in tacos, to accompany scrambled eggs…or wherever pickles are welcome.