Wash your jars well and sterilize them by either boiling them in hot water or by placing them into the oven to bake. That kills all the germs. Also boil your rubber rings.
Keep a pot with water to boil, add vinegar to it.
Place mushrooms into the boiling water and blanch them (cook a short time) for about 5 minutes covered. That kills off all the germs too.
Drain your mushrooms with a colander.
Prep your jars by placing the rubber gasket rings around the lid.
Place mushrooms into the jars.
Keep a pot with the water and salt to boil. This is your brine.
Pour hot salt water brine over the mushrooms in the jars. Cover the mushrooms with the brine. Close jars with the latches.
Keep the canning pot over a stove and place jars next to each other into the pot.
Cover jars in your canning pot with water and close the pot with the lid. Place thermometr in as per canner instructions.
Bring the temperature to 210° Fahrenheit/ 100° Celsius. This can take 30 minutes.
Keep the heat at 210° Fahrenheit/ 100° Celsius for another 30 minutes.
Take out jars when done and place on a clena kitchen towel to cool.
Once cooled store on a shelf in a cool and dry place.