Kohlrabi is one of those vegetables that can sit in a supermarket basket looking like a tiny alien spacecraft. Its swollen round stem may be pale green or purple outside, while the flesh is usually crisp and pale. Once you know what to do with it, it's surprisingly versatile: roast it like a root vegetable, steam it until tender or slice it thin for a crunchy slaw.
The important preparation step is dealing with the skin. Larger kohlrabi can have a tough fibrous outer layer, and leaving that on can spoil an otherwise well-cooked dish. The leaves can also be useful when fresh, but they cook differently from the bulb-like swollen stem.
Select a good kohlrabi
Choose a firm specimen without slimy patches, deep soft bruises or signs of decay. Smaller kohlrabi are often tenderer, while large mature ones may have more fibrous flesh.
The purple and green outer varieties usually have similar pale interiors. Colour alone doesn't tell you which one will taste sweeter.
If the leaves are still attached, look for sound fresh foliage. Very limp or yellow leaves may indicate it has been sitting around for a while.
Know which part you're eating
Kohlrabi is a member of the cabbage family. The rounded edible portion is a swollen stem, not a true underground root, though it is often cooked like one.
The leaves are edible when fresh and sound. They can be washed and cooked like other brassica greens, while thick stalks may need longer.
Do not eat parts that are visibly spoiled or mouldy. Trim ordinary dry edges, but discard extensive decay.
Wash and trim
Rinse the kohlrabi under running water, removing soil from grooves around the leaf stems. Cut away leaves and any woody stem ends.
Use a sturdy chopping board so the round vegetable doesn't roll while you slice it. Cut a flat base first if needed.
If the leaves are edible and fresh, wash them separately and store for a suitable cooked dish instead of automatically throwing them away.
Peel the tough skin
Use a vegetable peeler or sharp knife to remove the outer skin and any woody layer beneath it. Larger kohlrabi may require a thicker peel than young tender ones.
Check a thin cut slice. If you see a distinctly fibrous ring near the edge, remove more until you reach crisp tender flesh.
Don't waste enormous amounts of the vegetable without checking. Small fresh bulbs may have a relatively thin skin, while oversized ones can be more stubborn.
Cut into even pieces
For roasting, cut into cubes or wedges of a similar size. For boiling or steaming, moderately sized batons cook reliably.
A mandoline can make thin slaw slices, but it requires careful use and a hand guard. Kohlrabi is firm enough to cause injuries if it slips across an exposed blade.
Match the piece size to the cooking method. Tiny cubes can dry in a hot oven while thick wedges remain hard inside.
Roast kohlrabi for sweetness
Toss peeled cubes with a little oil, salt and pepper, then spread in one layer on a baking tray. Roast in a moderate-hot oven until the centres are tender and edges golden.
A starting point around 200°C conventional or 180°C fan suits many roasted vegetables. Depending on size, check after about twenty minutes and continue as needed.
A little browning gives kohlrabi a sweeter, nuttier flavour. Do not crowd the tray or the pieces will steam.
Boil until tender
Lower even pieces into boiling water and cook until a knife slides easily into the thickest part. Small cubes might become tender in around ten to fifteen minutes; thicker wedges need longer.
Drain thoroughly before seasoning. Kohlrabi can hold surface water, which may thin a sauce or make a mash watery.
For a lighter flavour, use a little butter, lemon and black pepper. It doesn't need a heavy cheese sauce to be worthwhile.
Steam kohlrabi
A steamer basket above simmering water is a good way to cook batons without submerging them. Cover and test regularly.
Steaming is convenient when you want tender kohlrabi for a vegetable bowl or as a side dish. It can preserve a little more firmness than a long boil.
Take care with hot steam and avoid stacking pieces too tightly in the basket.
Try a kohlrabi mash
Cook peeled cubes until very tender, drain well and mash with a little butter or olive oil. Add seasoning gradually.
Because kohlrabi has a different water content and texture from potatoes, the mash may be lighter and slightly more fibrous. You can combine it with potato if you want a creamier finish.
Don't add lots of milk before assessing the texture. You can always loosen a thick mash, but removing excess liquid is harder.
Sauté slices in a pan
Slice peeled kohlrabi thinly or cut into small cubes. Start with a little oil in a broad frying pan and cook until light colour develops.
A splash of water and a lid can help soften thicker pieces, followed by uncovered cooking to evaporate moisture.
Garlic, parsley and a squeeze of lemon make a simple finish. Keep the heat controlled so thin slices don't burn before they soften.
Can you eat kohlrabi raw?
Young tender kohlrabi can be eaten raw, peeled and sliced thinly. Its crunch is appealing in slaws with apple, carrot and a light dressing.
Wash it thoroughly and prepare with clean utensils. Raw vegetable dishes need suitable handling, especially when made ahead.
If a large bulb tastes woody, cooking it may improve the texture, but severe fibrous maturity won't necessarily disappear.
Cook the leaves separately
Wash the fresh leaves well and remove any exceptionally tough ribs. Chop them and add to a frying pan with a little oil and garlic, or steam like other greens.
They may cook much faster than the swollen stem. Adding both raw at exactly the same moment can leave one part overcooked.
Use only sound leaves, and refrigerate them promptly if not cooking immediately.
Flavours that work well
Kohlrabi has a mild brassica character. Dill, lemon, parsley, black pepper and butter suit it without overwhelming the flavour.
For roasted cubes, smoked paprika or a little cumin can add warmth. For slaw, a sharp yoghurt or mustard dressing balances the sweetness.
Don't assume it must taste exactly like turnip. The texture and flavour are related but different.
What if it stays hard?
Large chunks, low cooking heat or an exceptionally mature vegetable can all cause a stubborn centre. Cut pieces smaller and continue cooking gently.
If the surface has browned while the middle remains hard, lower the oven temperature or cover the pan briefly.
Don't use strong acids or bicarbonate as a shortcut to soften it. Size and time are easier to control.
The first recipe to try
Peel a firm kohlrabi, cut it into even wedges, coat lightly with oil and roast until golden and tender. Finish with salt, pepper and a little lemon.
It's a simple way to discover what the vegetable actually tastes like. From there, slaw, soup and mash become easy variations.