How to mince, dice, and slice onion (step-by-step guide)

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How to mince, dice, and slice onion - This step-by-step guide will show you how to master basic kitchen knife skills that everyone needs with an onion! Plus, you will learn how to pick them and where to use minced, diced, and sliced onion!

diced onion on top, sliced onion in the middle, and minced onion on the bottom

Onion is often the base of many dishes. Because of onion's versatility, I believe it is one of the best vegetables to practice your basic knife skill!

Before we learn how to mince, dice, and slice onion, let's discuss how to pick onion first.

How to pick an onion

These are what I look for when I pick onions at the store. You can apply these pointers to any type (yellow, Spanish, red, and white onion) of onions.

Firm - the onion should be firm and hard
No smell - a good onion should have no smell. If it has a strong onion smell, it might be rotten.
No sprout and a dry neck - the neck is the opposite pole of the root/beard part of the onion. The neck should be free from any sprouts and should be dry.
Papery outer skin - the onion should be free from any wetness thus the outer skin should be dry and papery.
No blemish - Onion should have no bruised or rotten spots.

How to prepare onion

two large yellow onions on a cutting board with a chef knife

Unless you are making onion rings, I use this method to prepare my onion.

By securely holding the onion with one hand, cut off the neck part of the onion.
Place the onion cut side down (this will ensure that the onion won't roll around), cut the onion in half.
Peel the very outer layer/skin of the onion.

Helpful tips on removing the rawness of an onion

If you like to add some raw onion to your salad or a burger, but don't like the rawness/spiciness of an onion? Place the sliced onion in ice water for 10 to 15 minutes. This process removes the rawness/spiciness of the onion significantly.

How to mince onion

half of a peeled onion on a wooden cutting board, small chunk of onion ready to be minced

very thinly sliced onion ready to be minced

Slice onion very thinly. You can slice them pole to pole (the neck part of the onion to the root/beard part of the onion) or parallel to the poles.
Fan out the thinly sliced onion on the board.
Chop them into small pieces. Cut downward against the slices. You may run your knife through the minced onion a couple more times to achieve the desired size.

Where to use minced onion

Fresh tomato salsa and guacamole
Tuna salad or chickpea salad

How to dice an onion

direct shot of half an onion cut parallel to the cutting board

straight shot of half an onion sliced parallel and perpendicular to the cutting board

Place the half-cut onion on the board. Place one hand on top of the onion. Carefully and gently, cut the onion parallel to the cutting board (make 2-3 horizontal cuts) starting from the neck to the root of the onion. Make sure you DO NOT cut all the way through the onion (first photo)
Now, make 4 to 6 vertical cuts from the part that's near the root but NOT all the way from the root to the neck. This will ensure that the onion pieces are still connected by the root (second photo).
Slice downwards against the vertical cuts you just made to dice an onion (photo below to the left).
When you are near the root of the onion, lay the onion in a way that faces the root upward so that it is flat on the cutting board. And dice them into the desired size around the root. Discard the root (photo below to the right).

Where to use diced onion

Stew or cacciatore (like my vegan creole sausage cacciatore)
Pasta (vegan creamy pasta primavera)
Noodle (vegan jjajangmyeon - Korean black bean noodles)
Curry (Indian style or Japanese curry)
Chili
Breakfast hash (vegan soy chorizo potato hash)

How to slice an onion

There are two different ways to slice an onion.

First is the slice parallel to the poles (left on the photo below). This is the shape that we are familiar seeing on a burger or in pickled onion. I do NOT recommend slicing this way when cooking the onion. As you can see in the photo below, this method produce different size pieces. Such will result in uneven cooking time.

Second way is to slice pole to pole/neck to root (right on the photo below). This is the way I like to slice my onion 99% of the time. Slicing pole to pole results in relatively similar size pieces and even cooking time.

sliced onion comparison - sliced parallel to the poles on the left, sliced pole to pole on the right

When slicing onion, you can remove the root/beard part of the onion first and slice. However, I find that removing the root at the end is easier. Because it helps keep the onion pieces intact while slicing. But it is totally optional.

straight shot of sliced onion from the bread part of the onion side

The challenge is slicing onion is to cut the onion in an angle towards the center of the onion. I like to make the cut near the root but not completely cutting through. This will help the root keep the onion intact and making the slices easy.

If you were to slice the onion straight down, making a vertical cuts, the middle part of the onion will be sliced. This will result in your end pieces to be big chunk. However, if you don't feel comfortable slicing onion in an angle, you can cut straight downward and cut the big pieces into thin slices/strips.

If you left the root intact, then cut off the root at the end.

overhead shot of sliced onion, the beard part of the onion removed

Where to use sliced onion

Korean pancake (vegetable pancake or kimchi pancake)
Noodle (Pad Thai or Japchae - Korean glass noodles)
Gyros (vegetarian seitan gyros)

There are many different ways but this is how I mince, dice, and slice onion! I find these methods to be the most efficient and easiest ways. I hope you find this information helpful!