Knife Skills: Diced Onion (or, Mirepoix 1)

If I have no idea what to make for dinner, I start by dicing an onion. It's one of the three ingredients in mirepoix (pronounced meer-PWAH), a flavor base for approximately every dish, ever. Ok, that's a hyperbolic statement, but you can't go wrong if you start with mirepoix, and therefore, onion. 

Choosing an Onion

For any type of onion, choose one which is nicely firm and has no soft spots. Green shoots coming from the top of red, white, or yellow onions are ok in my book; if you want to delay that, store your onions in the fridge.


It's helpful to think of an onion as a globe. By way of review, longitude lines go from pole to pole. Latitude lines run parallel to the equator. The north pole is the papery tip, and the south pole is the root bottom.

Prep: Sharpen and Hold

For the love of the Universe and your fingers, start with a sharp knife. Hold the onion with your  fingers curled (it helps to keep your fingernails short), and keep your wrist planted on the cutting board for stability.

Click on any of the images below for a larger version.

Step 1: Behead the north pole and be-foot the south pole

I often keep the north pole bit for vegetable or chicken stock. Be careful to only cut off the dry root bits of the south pole or all the layers of the onion will slip apart. You don't have to cut it off at all, but I find it a bit dirty and prefer to keep my cutting board clean.


Step 2: Bisect pole to pole and peel.

Not every onion is perfectly round. I aim to bisect in such a way as to get two even-ish halves - check out how even the reflection in your knife is. It should be reasonably easy to peel away the dry, papery bits now. If it's not easy, try running the onion under some cool water. Sometimes you'll get a layer with a partially papery bit - just peel away the whole layer. Stock (or compost) fodder!

Step 3: Longitudinal, horizontal slices

  • Place the flat side of the onion down, and set your palm firmly on top of the round bit. Flex your fingers out of the way.
  • Turn your knife parallel to your cutting board.
  • Starting close to your board, make a few (or many, depending on your desired dice size) slices through the onion, creating a few "stories".
  • STOP SLICING before going through the south pole.

Step 4: Longitudinal, vertical slices

  • Turn your knife back perpendicular to your board, and point the tip towards the south pole.
  • Keeping the tip just shy of the south pole, make a few (or many) slices, creating walls for your stories.

Step 5: Latitudinal, vertical slices 

  • Turn your knife one last time so it's parallel to the latitude lines.
  • Make thin slices along the latitude lines, keeping your fingers curled in and your wrist on the board.
  • When you get towards the end, turn the south pole bit onto the board and make a few more slices. 
  • Toss the south pole end with your stock (or compost) bits.
  • If you need an even smaller dice, run your knife several times through the pile of onion.

Dicing complete! I can dice an onion in about 45 seconds, and I'm not even a pro. Sharp knife + practice = safe speed and reduced opportunity for "onion eyes". Happy dicing!