Slice or chop the prepared beets to your desired size. Add them to an airtight container and set them aside while you make the brine.
Combine the water, vinegar, sugar, salt, mustard seeds, and peppercorns in a small saucepan set over medium heat.
Bring the mixture to a boil and cook until the sugar and salt have dissolved.
Pour the brine over the beets, making sure to cover them completely.
Seal the container and place it in the fridge to chill. I recommend waiting until the beets are fully chilled to serve, but they will have a lightly pickled flavor after 15 minutes.
Store the beets in an airtight container in the fridge for up to two weeks.
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Notes
This recipe works with canned, boiled, steamed, or roasted beets! Roasting the beets before pickling really concentrates their flavor while boiling/steaming tends to be a bit easier and quicker-- feel free to do what works for you!
To roast the beets, wash them and remove any greens. Drizzle them lightly with olive oil and wrap them in foil. Place the beets on a baking sheet and bake in a 400F oven for 45 minutes or until a paring knife slides in and out of the beets easily. Allow them to sit for 5 minutes, then carefully peel the skin away from the flesh and cut as desired.
To boil the beets, bring a large pot of salted water to a boil. Trim and wash the beets. Add the beets to the boiling water and cook for 30 minutes, or until a paring knife slides in and out of the beets easily. Remove the beets from the boiling water and place them into a bowl of ice water. Peel away the skins and cut as desired.
Water helps the sugar and salt dissolve in the brine. If you don’t have enough brine to completely cover your beets in the jars, feel free to use additional water.
I’m using apple cider vinegar because it pairs perfectly with beets, although you can use almost any clear vinegar to pickle-- white vinegar, rice wine vinegar, white wine vinegar, etc.