Most cooks treat the fat on a piece of lamb as something to trim off, render out or leave on the plate. That is a missed opportunity. Lamb fat is one of the most flavourful cooking fats available, and it behaves quite differently from beef fat, pork fat or butter.

Used well, it improves roast potatoes, enriches pastry, seasons slow braises and adds real depth to everyday cooking. It is also one of the cheapest ingredients you can buy from a producer, because most people do not know what to do with it.

What makes lamb fat different

Lamb fat has a distinctive flavour, and it comes from the branched chain fatty acids that accumulate in ruminant fat, particularly in older animals. In young lamb the flavour is mild and pleasantly savoury. In older animals it becomes stronger.

It also has a higher melting point than most other animal fats. Lamb fat is firm at room temperature and does not liquefy until around 44 to 55 degrees. This has consequences for eating and for cooking.

For eating, it means lamb is best served hot. Fat that cools on the plate can solidify and feel waxy in the mouth. Warm plates and prompt service fix most of this.

For cooking, it means lamb fat is stable, firm to handle and excellent for high heat roasting.

Types of lamb fat

Understanding what you are buying helps.

• Subcutaneous fat. The layer under the skin, forming the fat cap on legs, shoulders and racks. Firm, white and clean tasting

• Intermuscular fat. Fat between muscles, found around the shoulder and in the seams of larger cuts

• Kidney and cavity fat. Harder, more brittle and traditionally prized for rendering into clean tallow

• Fat trimmings. A mix from butchery, sold specifically for rendering or cooking

Note that this is different from beef suet, which comes from around the kidneys and has different properties. Lamb trimmings are a mixture, and the label matters when you follow a recipe.

Rendering lamb fat into tallow

Rendering turns raw fat into clean, shelf stable cooking fat. It is easier than it sounds.

Method.

Chop the fat into small pieces, or freeze it briefly and mince it, which speeds up rendering

Place in a heavy pot or slow cooker with a splash of water, which prevents scorching at the start

Heat gently, around 100 to 120 degrees, stirring occasionally, for two to three hours

As the fat melts, the water evaporates and small solid pieces darken and sink

Strain through a fine sieve or muslin into a clean jar

Cool and store in the fridge, where it keeps for months, or freeze for longer

Keep the heat low. Fat rendered too hot takes on a burnt, bitter flavour. Patience is the entire technique.

The crisp brown remnants, called cracklings, are delicious salted and eaten warm, or scattered over salads and flatbreads.

What to do with rendered lamb fat

Roast potatoes. Toss par-boiled, roughed-up potatoes in melted lamb fat before roasting at high heat. The result is a crunchy, deeply savoury crust that goose fat fans will recognise.

Frying eggs and vegetables. A spoonful in the pan adds a savoury note to onions, cabbage, root vegetables or a fried egg on toast.

Flaky pastry. Lamb fat makes a tender, flavourful crust. Excellent for pies with lamb, mushroom or root vegetables. Use it in place of half the butter.

Flatbreads and dumplings. Traditional in Central Asian and Middle Eastern cooking, where lamb fat is prized. A brush of tallow on a flatbread transforms it.

Searing meat. Lamb fat has a good smoke point and adds flavour to a steak or chop as it sears.

Confit. Slowly poaching shanks or shoulder in lamb fat is a classic preservation technique.

Spiced rice and pilafs. Frying onions in lamb fat before adding rice gives a rich base for biryani, plov and similar dishes.

Cooking with the fat on the cut

You do not need to render anything to use lamb fat well. Simply cook the meat with the fat on.

Score the fat cap. Cut a crosshatch pattern through the fat, not the meat, before roasting. This lets it render and crisp rather than sitting in a soft layer.

Start fat side down. For chops, racks and leg steaks, begin over moderate heat, fat side down, and let the fat render before turning. You end up with crisp fat, a well browned surface and a cooking medium made from the meat itself.

Leave more on for long cooking. Shoulder, shanks and breast benefit from retaining fat. It bastes the meat from within and keeps it succulent.

Trim heavy external fat for lean cuts. For quick grilling, leave a thin layer and remove any thick or uneven deposits that would cause flare-ups.

Dealing with the strong flavour

If you are sensitive to lamb's distinctive taste, several things help.

• Choose young lamb. Flavour compounds increase with age

• Trim more fat and render out the rest

• Pair with acid. Lemon, vinegar, yoghurt and pickles cut richness

• Use strong aromatics. Garlic, rosemary, cumin, mint and sumac balance it

• Serve hot. Cooling emphasises the waxy character

Rendering also mellows the flavour. Clean, strained tallow is milder than raw fat, especially if the fat came from a young animal.

Storing and using tallow

• Fridge: three to six months in a clean airtight jar

• Freezer: a year or more

• Keep it dry and clean. Any water or food particles shorten shelf life

• Label the jar so nobody mistakes it for something else

Scoop out portions as needed. It behaves like solid coconut oil, firm but easily scraped.

Nutrition and moderation

Lamb fat is mostly saturated and monounsaturated, with a modest omega-3 contribution that is higher in animals finished on pasture and forage crops. It is an energy dense ingredient, best used in small amounts for flavour rather than as a bulk cooking medium.

Buying the fat

Some producers sell fat trimmings alongside the meat, often at a very low price per kilogram. If you cook regularly, it is worth adding a bag to an order. Ask whether the fat comes from grass fed animals, since flavour and fatty acid profile reflect the diet.

Rendering a batch once a month gives you a jar of high quality cooking fat for a fraction of what specialist tallow costs.

Fat is a reminder that good lamb has more to offer than the obvious cuts. Learning to use all of it makes you a better cook and a more efficient buyer.

Matangi Prime Meat sells grass fed lamb fat trimmings alongside its Hawke's Bay lamb range, clearly labelled as different from beef suet.