The way to get clean, even pieces of chocolate is to lay the block flat and slice it with a large knife in a sawing motion; holding the blade upright and pressing straight down breaks the chocolate into uneven chunks and sends shards flying. Chocolate cuts most cleanly at around 18-20°C room temperature.
Grating calls for the opposite approach: chilling the chocolate in the fridge for 15-20 minutes before you start keeps it from melting from the heat of your hand. Chocolate that hasn't been chilled turns soft and sticky under the grater and clogs the holes.
How do you chop chocolate with a knife?
Start a heavy chef's knife at the edge of the block and draw it back and forth in a sawing motion. The weight of the blade does most of the work; pressing down harder just makes the chocolate crack in unpredictable places. Splitting a thick block in half first, then slicing thinner pieces from each half, gives more even-sized pieces overall.
In a warm kitchen, chocolate can soften and stick to the blade; wiping the knife with warm water now and then cuts down on the sticking. In a cold kitchen the block gets too hard and fine shards fly everywhere when you cut it — which is why 18-20°C is the sweet spot.
If a recipe calls for evenly sized chopped pieces, marking the block with a ruler, or simply aiming for consistent slices by eye, makes a real difference; uneven pieces melt at different rates, so some can scorch while others are still solid.
Why does grating chocolate become difficult, and how can it be made easier?
The biggest problem when grating is the heat your hand transfers to the chocolate; as your fingers touch the block, the surface starts melting and leaves a film on the grater. Wrapping the block in a paper towel while you hold it, on top of chilling it, keeps your hand from touching it directly.
For a fine, powdery grate use the small holes; for thick curls use the large ones — mixing the two won't give you the texture you're after. Grated chocolate that won't be used right away should go in a sealed container in the fridge; left out, it picks up moisture and clumps.
Why does chopped chocolate sometimes turn white?
Chocolate pieces held in a warm hand for too long, or left on a warm counter, can turn a dull white as the fat on the surface separates and re-crystallises. This doesn't affect the taste, only the look, and it disappears once the chocolate is melted and set again.
Shortening how long your hand touches the chocolate while chopping is the most practical way to prevent this. Transfer the cut pieces to a bowl right away and handle them as little as possible.
How do you keep chopping and grating tools clean while working?
Once chocolate residue dries on a knife or grater it's hard to scrape off; wash the tools in warm water right after use, while the chocolate is still soft. Trying to wash it with cold water lets the hardening residue lodge in the holes and edges.
If the same grater was just used on something salty or spiced, rinse it thoroughly before using it on chocolate, or you'll pick up a stray flavour in the grated chocolate.
Knives and graters with wooden handles shouldn't sit in water for long; wood absorbs moisture and can crack over time. Drying and airing these tools right after washing is better both for hygiene and for how long the tool lasts.