Wash cauliflower, cucumber, and onions in cold water, then drain vegetables well.
Cut cauliflower into bite sized florets, peel the cocktail onions, and slice cucumbers into ¾-1" thick slices. If you have a wavy slicer, feel free to use that for authenticity! Place all of the vegetables into a large bowl.
Fill your LARGE pot - or hot water bath canner - with at least 6" of water - you’ll need enough water to cover the jars - put on medium or high heat to bring it to a boil as you prepare your brine.
In another pot (NOT the large canning pot!), combine vinegar, water, and dry ingredients (sugar, salt, mustard powder, and turmeric). Bring to a boil, stirring well to dissolve the salt.
As brine is coming to a boil, cut two large squares from the cheesecloth, stack on top of each other.
Measure the pickling spice into the center of the cheesecloth, draw edges of cloth in to enclose the spices, tie into a tight little package with the twine.
Once brine comes to a boil, add spice package and boil at a low boil for 10-15 minutes, to taste.
Once it tastes right to you, remove the spice packet. Add vegetables, stir well, and boil for 10 minutes.
Remove a little of the brine, mix Clear Jel into it until smooth. Add a little bit more brine if necessary to get it to a pourable consistency, add it all back into the pot and stir well. Bring to a full boil for 5 more minutes.
After 5 minutes, turn the heat off.
Use a sterilized canning funnel and sterilized ladle to scoop hot pickles and sauce into sterilized canning jars, leaving about ½" head space.
Wipe off the top edges of the glass jars with a clean, wet towel, top each with a new, sterilized lid, and carefully screw on a clean lid ring. I like to use a kitchen towel for this, the jars are HOT!
Carefully place your jars of pickles into the boiling water pot, allow to process pints for 15 minutes. CAREFULLY remove the hot jars, allow to cool overnight at room temperature.
The next day, check to make sure that all of the jars achieved a proper seal – try to push down in the middle of each lid. If it “pops”, it did not seal.
Any jars that didn’t seal should be put in the fridge and used in the next few weeks - refrigerator pickles.
Properly sealed pickles are safe for long-term storage, outside of the fridge. Store in a cool, dark area (ideally) for up to 1 year, chill well before eating.