Weights & Measures
Recipes should always specify the weight of onions "as purchased"
presuming a standard amount of loss from peeling. The U.S. National
Onion Association defines a medium onion to be 5 ounces. Onions that
small are hard to find in Southern California onion bins, so I would
prefer 6 ounces, which produces 1-cup chopped small. What recipe writers
in England or Bangladesh consider a "medium onion", I haven't a clue, but
in southern India shallots are often called "small onions".
|Small||4 oz - 5 oz ||1/2 cup|
|Medium ||5 oz - 7 oz ||1 cup|
|Large||7 oz - 10 oz ||1-1/2 cup|
Buying & Storing Onions
Selection: You will want several sizes of yellow onions to fit
various recipes, and perhaps some other varieties: White, Red, Sweet,
depending on the recipes you are working with (see
Onions for details). When buying onions
always press on the top right by the stem. If the onion is not hard
there, it is starting to decay inside. Onions that have started to
sprout should be discarded as the central layers will be depleted.
Storage: Yellow storage onions (the most common type)
last around a month stored in cool dark place with good air circulation
- a bin or mesh bag. Red and White onions will usually keep almost as
long, but Sweet onions are much more perishable, figure on just a couple
of weeks at best.
Cut Storage: Unused peeled and cut (but not sliced or
chopped) onions can be kept in the fridge in a plastic bag for several
days, but beyond that they are subject to mold and other forms of
Peeling, Cutting & Chopping Onions
This is the big problem with cutting onions. When damaged, the cells
of Onions release enzymes which combine with sulphur compounds to produce
propanethiol S-oxide vapors. When these reach the moisture in your eyes
they form Sulphuric Acid, which stings, causing increase in tear
production to wash it away. Some onions are much worse than others, it
depends on how much sulphur was in the soil they grew in. There are
various techniques for reducing this effect, some practical, some not.
- Knife: It is very important to use a very thin, razor
sharp knife to minimize damage to the onion cells. A thin
Santoku (shown above) is ideal -
better than a Nakiri because it has a point, which makes it possible
to accurately prepare an onion for chopping (see below). You should
have one anyway because it is the premier vegetable slicing knife -
and it doesn't have to be endorsed by a celebrity chef and cost $200.
For details on keeping it sharp see our
Sharpening Knives page. With care you should need only to use a
- Stand: When cutting onions, keep your eyes as far from
the cutting as possible.
- Clean: Remove all onion debris and cut onion from in
front of you right away and wipe the cutting board with a sponge now
- Fan: Blowing the vapors away from you is certainly
- Swim Goggles: This will certainly work. Some chefs
report using a full snorkel mask when they cut a lot of onions.
- Refrigerate: Cooling the onions slows the enzymes that
cause the problem. Unfortunately, it requires an improbable degree of
planning ahead - I certainly don't do it.
- Water: Many sources suggest cutting onions under water.
That would certainly work, but I have failed to think of any way that
can actually be done, and especially done safely.
Peeling & Cutting
- Rings: If you need full rings, it is best to use
sweet onions, particularly ones of a flattened shape because they
provide the best yield. Just cut off some a the stem end, peel the
dry and semi-dry layers over the root end to use as a handle. Slice
crosswise, usually about 1/4 inch wide.
- Unless you are cutting full onion rings, which I very rarely
do, first cut the Onion in half lengthwise. This makes it very easy to
work with, and also you find immediately if your onion has internal
- Place onion on your board, cut side down, and cut off a little at
the stem end. NEVER cut off the root end - you need it to hold
- Peeling: Pull back the dry and semi-dry layers over
the root end. Some people leave them on as a handle, but I usually
don't. Generally, you peel off the minimum, because the outer layers
are the most nutritious - but - IF you will be frying until
golden, or especially darker, you may have to peel an extra layer
so all your onion has the same water content.
- Slicing: The Onion is now ready to slice crosswise
as thick as you want. I usually want quarter slices, easier to
handle in cooking than half slices, and much easier than rings. To
do this I make one cut down the center to near, but not through
the root end. Just slice crosswise using the root end to hold on to
when you get near it.
- Chopping: Make lengthwise slices as in the first
photo to the right - almost to the root end but not through it.
Make them very close together for chopping fine, less close for
chopping small or medium, and quite wide for "dice". Tilt the knife
at an angle to cut inward for cuts on the sides, and be careful not to
cut all the way so the onion stays together. Again, a very thin, razor
sharp knife is essential - note that the cuts barely show in the
- Now slice crosswise, holding the onion from the sides and moving
your fingers back as you slice, until you get near the root end, then
hold by the root end. Slice very thin for chopping fine, not so thin
for small or medium and wide for dice. The second photo to the right
shows the result. This is usually all the chopping the onion will need.
Of course, it won't pile up neatly as in the photo.
Note that some writers say to make one or more horizontal cuts
through the onion. I find this dangerous, and entirely unneeded if you
tilt the knife to cut inward as you work the sides.
Disarming Chopped or Sliced Onions
Particularly for use as a condiment, you may wish to tame chopped
or sliced onions. There are two methods. First is to soak them in cold
water for 20 minutes or so, then drain completely. The other is to give
them a quick dip in rapidly boiling water, then quench in cold water
Frying is by far the most common method of preparing onions for a
recipe. Frying onions takes close attention, because if you screw them
up, the recipe is doomed from the start.
Most commonly, onions are fried until "translucent", at which stage
they've lost their harsh bite and are somewhat soft - but before
there is any browning. "Golden" is the next most common level, then
"browned", and "dark browned", the least common and most difficult.
Even a small amount of burning will impart a bitter taste to the recipe.
Of course, a former girlfriend from Texas preferred a modest amount of
burning because that's how her mother used to make them.
- Peel, slice, dice or chop as appropriate for the recipe. If you
will be frying beyond "light golden", be sure you have peeled deep
enough that all the onion has the same moisture content.
- Select a pan that is quite a bit larger than the burner, usually
a multi-ply sauté pan or deep skillet. 2 quart and 3-1/2 quart
sauté pans should be full wrap-around multi-ply because slab
bottomed will have a very hot ring at the edge of the slab. This makes
control of even browning difficult. A 5-1/2 quart is so much bigger
than the burner that a slab bottom pan works fine (and is much more
affordable). For details see our Stainless
Steel & Multi-Ply page. Cast Iron cookware doesn't have so much
of this problem and fries more evenly.
- Use the amount of oil specified in the recipe. It doesn't need to
be a lot, but 1 Tablespoon is about minimum for a 3-1/2 quart
sauté. More oil makes for easier control.
- Start on fairly high heat, and stir very often, turning away from
the pan for only very short times, but don't stir continuously, let the
onions rest a little between stirrings. In particular move onions at
the edges toward the center, and vice versa, and scrape down the sides
as onions stuck there will darken very rapidly. As the onions fry, keep
turning the heat down. Once they start to color they should be on rather
- For darker browning, you need very low heat and a lot of attention,
because any burning can seriously affect your recipe results.
Very Even Medium or Dark Browning
This is particularly important for Onions or Shallots that are used
as a garnish. This technique will also make it easy to fry onions very
dark without so much risk of some burning.
- Peel the onion deep enough so all layers have the same moisture
- Slice or chop the onions to the size desired. Remember that the
onion pieces will shrink quite a lot. Keep the size as uniform as
- Spread them out on a hard surface to dry. Turn them now and then
for even drying. About 6 hours will do.
- Fry them in fairly shallow oil, over rather low heat, stirring very
often but not continuously.
- If your recipe calls for them to be crisp, don't try to fry them
crisp, they should still be a bit flexible. They will crisp up as they
- Drain on paper toweling.
Pearl Onions &
Handling these like full size onions would be very tedious. They are
almost always used whole. Commercial pearl onions aren't actually real
pearl onions (see Pearl Onions),
they're selected regular onion types grown under crowded conditions to
keep them very small.
- Bring plenty of water to a rolling boil.
- Pour Onions into the boiling water over high heat. Don't overload
the pan. Leave for about one minute, then fish them out and quench
under cold water (easiest to toss them in a big bowl of cold water
with the faucet running into it).
- With a razor sharp knife, cut a little off the stem end. Then peel
the paper layers back over the root end.
- Cut off the absolute minimum from the root end - it's what holds
the onions together while cooking.
Oven Roasting Onions
Onions may be oven roasted whole unpeeled, halved crosswise unpeeled
and dressed on the cut side, halved, peeled and dressed on the cut side,
and cut into wedges.
For whole and half onions the oven is preheated to
425°F/220°C. For wedges or small half onions, the oven is
preheated to 400°F/200°C.
Onions to be roasted are usually tumbled with some Olive Oil. Half
onions are usually painted with Olive Oil on the cut side and often
dressed with herbs or spices. Wedges are usually tumbled with an oil
Onions can be placed on a baking sheet, oiled or not, but for easy
clean-up, the sheet can be covered with foil, oiled or not. Roasting
time will be about an hour for whole onions, depending on size. They are
done when a sharp skewer finds them soft all the way through. Halved
onions are usually roasted until lightly browned on the cut side.
Whole onions are often sliced in half after baking. Slice them
lengthwise, not crosswise, with a very sharp thin knife.
Finished roasted onions are often dressed with balsamic vinegar or
wine vinegar and olive oil, and perhaps a touch of salt. Herbs are also