- Peel and slice the onions: Remove the outer skin of the onions and slice them into uniform pieces using a sharp knife or mandolin. You can choose to cut them into rings or use chopped onion, depending on your preference.
- Spread the thin slices out on the parchment-lined baking sheets in a single layer.
- Next, place the onion pieces in the oven at its lowest temperature around 130-150ºF/54-66ºC.
- If your oven doesn’t go as low as that, use the lowest temperature and prop the door open with a wooden spoon handle, so the steam can escape while the onion dehydrates.
- Check on the onion hourly, flipping it over a couple of times, to dry it faster.
- Depending on how thin and uniform your onion slices are, you can expect it to take about 6-10 hours to dry onions.
Grinding the Onions into Powder
- Once cool, the onion slices should snap. If not, put them back into the oven again.
- Once the dried onions are ready, transfer them into a spice grinder or food processor.
- For minced onion or onion flakes, you’ll pulse the grinder until it’s at your desired consistencey. For a finer texture and smooth powder, continue grinding for longer periods of time.