Slice all the onions into 1/4″ slices. A mandolin comes in handy for this. Place in a large bowl.
Whisk together the olive oil and balsamic vinegar. Pour over the onions and with your hands mix and mix and mix. Be sure to coat each onion. Cover and place in refrigerator for 24 hours to marinate.
Place a mesh colander inside of a large bowl and drain the marinade sauce off the onions. Place the onions on the teflex dehydrator sheets and dry at 110 for 4-6 hours. Or until they soften and take on a cooked appearance.
