Step 1

Wash and dry the jars and cucumbers: Wash 2 wide-mouth pint jars and their lids in hot, soapy water. Set them aside to dry.Rinse the cucumbers well under cold water, pat them dry, and then set them on a towel to dry completely.

Step 2

Slice the cucumbers and onion, then pack them in the jars: With a sharp knife or a mandoline slicer, slice the cucumbers and onion into slices 1/8- to 1/4-inch thick.Firmly pack the cucumbers and onions into the jars, fitting in as many as you can without smashing the vegetables. Leave 1/2-inch or so of headspace at the top of the jars.

Step 3

Make the brine: In a small saucepan over medium-high heat, bring the vinegar, water, sugar, salt, and pickling spice up to a simmer. Stir occasionally and continue simmering until the sugar and salt are dissolved.

Step 4

Pour the brine over the vegetables: If you have a canning funnel, use it here to make it easier to fill the jars. Carefully pour or ladle the hot brine into each jar, filling the jars until the cucumbers and onions are covered. It's ok if a few small pieces poke out the top.

Step 5

Cool and refrigerate for 24 hours: Screw on the lids, then let the jars cool to room temperature (about an hour). The cucumbers will start off bright green, but will become darker and more "pickle-colored" as they cool.Place them in the refrigerator. Wait at least 24 hours before eating the pickles in order to let the flavors develop. Use them within one month.