Start by washing all your vegetables thoroughly. Trim the cauliflower into small florets, dice the celery, carrots, bell peppers, jalapeño, and serrano peppers into small pieces. Mince the garlic cloves finely. Place all these prepared vegetables in a large mixing bowl.
Drain the can of green olives, reserving the juice. Chop the olives into smaller pieces and add them to the bowl with the other vegetables. The olives will add a unique briny flavor to the mix.
In a separate bowl, combine the reserved olive juice brine, white vinegar, olive oil, avocado oil, dry oregano, celery seed, and coarse salt. Whisk the mixture until the salt has dissolved and everything is well combined.
Pour the brine over the vegetable mixture, ensuring that all the vegetables are coated. Stir gently to combine everything evenly. The brine not only flavors the veggies but also helps in the pickling process.
Transfer the giardiniera mixture into sterilized glass jars, pressing down lightly to remove any air pockets. Ensure that the vegetables are submerged in the brine. Seal the jars tightly and store them in the refrigerator.
For the best flavor, let your giardiniera sit in the refrigerator for at least 24 hours before using it. This allows the flavors to meld and enhances the overall taste. The longer it sits, the better it gets!