When chopping vegetables, please don’t start hacking away randomly, hoping for the best. It’s a sad truth, but chopping is pretty much the most important thing you can learn to do in the kitchen. Doing it right will save you time; a whole lot of pain, and blood; and will make your food cook, and taste better. It’s worth taking the time to learn how to do it efficiently and safely.
The first thing to know about chopping, of course, is what kind of knife you should use. The best knives are like these ones, with a long, wide blade — there should be enough room, that when the knife blade is fully resting on the cutting board, your fingers aren’t pinched. This ensures you can chop rapidly, without bruising your knuckles. Also, don’t use a serrated (sawtooth) edge for chopping, or a small knife if possible. Longer knives give you more leverage. Notice that the top two knives have curved blades — this is the most efficient for chopping (the top knife especially probably gets used twice as much as any of the others.)
And make sure the knives are sharp. Paradoxically, you’re way more likely to cut yourself with a dull knife, because you have to force it, and it will often not cut straight. The best way to tell if a knife is sharp, is the famous “tomato squish test”. If you can actually cut, not squish, a ripe tomato, you’re probably okay.
The goal of chopping is to get your food to the size you want, with a minimum of cuts, and with your fingers safely out of the way. Your food, like pretty much everything else, is three dimensional, so to get cubes the size you want, you need to make cuts along three axes.
Some foods are easier or harder to chop than others. Because herbs are flat already, they’re pretty easy. You can cut them into strips (thin strips of herbs are called a chiffonade), or chop them. Onions are also kind of easy, but only once you get the hang of them. Because they’re already detached along one axis (the nested rings), you just need to cut once, into strips, and then a second time into cubes.
Garlic is, again, the same general principal. You want to get the peel off, then cut it into either slices, or mince. Because we use garlic so much, and it’s a little tricky to get it small, and to get the peel off efficiently, we wrote a separate guide for this.