One of the most enjoyable aspects of fermenting food (as compared to other techniques, such as waterbath or pressure canning), is the freedom to be ultimately creative and to experiment in the kitchen.
My early experiments in fermenting were almost always either overly salty or under-fermented. I’ve learned that using 15-30 grams (approximately 0.5-1 ounce) of salt per 1 liter (1 quart) mason jar, is the right amount of salt for me and that regular tasting ensures success in fermenting. A ferment can quickly migrate from under-fermented to perfect and then to over-fermented in less than a day (depending on the temperature and what you’re fermenting).
I also love to cook with mirepoix – the classic French combination of onion, carrot and celery. It’s fantastic as a base for stir fry, sauces, soups and more. We found ourselves with an awesome bunch of onions, heirloom carrots and soup celery (its late harvest celery that’s very tough to eat but has an abundance of leaves that can be used like celery hearts). I couldn’t resist fermenting them together:

Some of the carrots were purple (on the outside) which explains some of the colors in the photo.
I mixed 2 cups of chopped mirepoix with 15 grams of salt in a large bowl and then ‘crushed’ it with my hands. I alternated between kneading the mixture (like you would with bread) and crushing it in my fists. This helps break the cell structure down which assists the salt in pulling liquids out of the vegetables.
I left the mixture overnight, covered with a towel (although I’d use a reusable coffee filter like this now that I’ve learned the trick). I also set a jar full of water to the side to evaporate the chlorine (which can prohibits fermentation).
I checked the mixture the next morning – the jar was partially filled with liquid. I then added enough liquid to comfortably cover the vegetables by about a half an inch.
I then placed an airlock on the jar and let it sit for 11 days on the kitchen counter (the airlock prevents any mold).
It tastes a whole lot like mirepoix – only it has some lovely umami/ sour undertones and a slight bit of sour that comes from fermentation. It’s not overly sour and I plan to use it just as I would a mirepoix (although I won’t need nearly the same amount as the process has intensified the flavors).
This will keep in our fridge indefinitely, which is extremely handy for busy nights were cooking time is limited. I expect we’ll be eating this very shortly – and then making it again.
Would you try this or have you made something similar? We’d love to hear about it!