The knife hand
You shouldn’t exert too much downward pressure. A knife is not an axe, so don’t hack down at the food and make that rat-a-tat noise that most amateurs do. You should use a gentle rocking motion – more like a handsaw than an axe. Gee, this is too difficult to explain in words. Have a look at this YouTube video for a good demonstration of how to do it. Note also the chef’s other hand while you’re there.
The guide hand
Anyone who regularly watches cookery shows on the telly will have noticed that cutting is a two-handed process. Assuming you’re right-handed, you hold the knife in your right hand and use the left to hold the food and help to guide the knife so that the pieces of food are evenly cut. This not only means that the food looks more attractive, it also means that the food will be cooked more evenly. The assisting hand is often referred to as the guide hand, although some chefs refer to it as the holding hand.
Notice how, in the video above, the chef keeps his fingers together and curls them under to keep them out of harm’s way. This is a good habit to get into and will help you to avoid hacking off bits of fingers on your guide hand.
Practice makes perfect
Get a heap of carrots and leeks or whatever and practise your knife skills using this rocking technique. You can always make soup with the veggies afterwards. It’s like any other skill, it doesn’t just happen on day one. You need to practise a bit until it becomes second nature. Take it slowly at first – don’t take any risks with your fingers, they’re very valuable assets! The speed will come in time, I’m sure of it.