Ingredients

Equipment Needed

• •Large preserving pan or wide, heavy-bottomed stockpot
• •Long wooden spoon
• •Sugar thermometer (optional, for the cautious)
• •Jam funnel
• •4 sterilised jam jars with tight-fitting lids
• •Small square of muslin and kitchen string

Instructions

1. 1

   Salt the marrow overnight

   Layer the cubed marrow in a large bowl, scattering each layer with the sugar as you go. Cover with a tea towel and leave on the side overnight, somewhere cool. By morning the marrow will have wept out an astonishing amount of liquid and the sugar will have half-dissolved into a thick, pale syrup. This step matters. It draws the water out before the cooking begins, which is the difference between jam and soup.

   A big bowl. Bigger than you think. The marrow looks like a lot until the sugar starts pulling the water out of it, and then it looks like more.
2. 2

   Tip everything into the pan

   Scrape the marrow and all its syrupy liquid into a wide, heavy preserving pan or your largest, deepest saucepan. Add the lemon zest and juice, the chopped crystallised ginger, the grated fresh ginger, and the ground ginger. Tie the lemon pips and any membrane in a small square of muslin and drop it in too. The pips carry pectin, and marrow has none of its own.

3. 3

   Bring up slowly

   Set the pan over a gentle heat and stir until any remaining sugar has melted into the liquid. You should see no grit on the wooden spoon when you draw it across the bottom. Only then turn the heat up and bring the whole thing to a steady, rolling boil. Rushing the sugar before it dissolves is how you crystallise a jam, and there is no coming back from that.

4. 4

   Boil and watch

   Let the jam boil hard for an hour, sometimes a little longer. Stir now and then with a long wooden spoon, especially towards the end, when the sugar starts to catch. The marrow will go from pale and opaque to a deep amber, almost honeyed, and the cubes will turn translucent and glassy. The kitchen will smell of hot sugar and ginger, sharp and warming, like the inside of a Christmas tin. Trust your nose. It knows before you do.

5. 5

   Test for set

   Put two or three saucers in the freezer before you start, so they are properly cold when you need them. To test, take the pan off the heat and drop a teaspoon of jam onto a cold saucer. Wait half a minute, then push it with your fingertip. If the surface wrinkles, it's ready. If it slides about like syrup, give it another five minutes and try again. Marrow jam will never be a stiff set. You're after something soft, spoonable, like loose honey. Don't chase a setting that isn't coming.

   Take the pan off the heat while you do the wrinkle test. If you leave it boiling, you'll overshoot, and overcooked marrow jam goes sticky and dark and loses its perfume.
6. 6

   Jar and seal

   Fish out the muslin bag and squeeze any liquid back into the pan. Let the jam stand for ten minutes off the heat so the cubes settle through the syrup rather than floating to the top of the jars. Ladle into hot, sterilised jars, right up to the brim, and seal at once. Label them when they're cool. Write the date on. You'll thank yourself in February.

Chef Tips

• •Use a marrow that's properly mature but not yet turning. You want pale green skin, firm flesh, seeds you can scoop out cleanly with a spoon. If the seeds have gone hard and woody, the marrow is past it and won't make good jam.
• •Crystallised ginger varies wildly. Get the best you can find, the kind that is soft and properly fiery, not the cheap, sugary lumps that taste of nothing. This is a jam where the ginger is the whole point, so don't economise on it.
• •If the jam seems slow to set, don't panic and don't keep boiling. Marrow has no pectin of its own, which is why the lemon pips go in. A soft set is the right set here. Anything stiffer turns leathery and loses the perfume.
• •Wonderful on hot buttered toast, but don't stop there. Spoon it over a wedge of cheese, especially something sharp like a proper Cheddar or a piece of Lancashire. Stir a spoonful into the pan when you're cooking pork. Drop a teaspoon into a mug of hot water on a cold afternoon and call it a tonic.

Advance Preparation

• •The marrow must be salted with the sugar overnight before cooking. Don't try to skip this step or the jam will be too watery to set.
• •Sterilise the jars while the jam is on its final boil. Wash them in hot soapy water, rinse, and put them in a 140C oven for fifteen minutes. The jam goes into hot jars, never cold ones, or the glass will crack.
• •Sealed properly, the jam keeps in a cool, dark cupboard for a year. Once opened, refrigerate and eat within a month, though it rarely lasts that long.

Frequently Asked Questions

Nutrition Information

1 serving (about 20g)