Peel the marrow and cut it in half. Scoop out and discard the seeds. Cut the ﬂesh into 1–2 cm pieces and put them in a bowl in layers, sprinkling each layer with some of the salt. Cover the bowl and set aside for 24 hours.
Next day, rinse the salted marrow under cold running water, drain well and set aside. Peel and chop the tomatoes, peel and chop the onions and peel, core and slice the apples. Put them in a large preserving pan with the vinegar, stir well, bring to the boil on medium heat, then reduce the heat and cook on low heat for 30 minutes.
Add the dates, brown sugar, mustard seeds, ginger, allspice, nutmeg and marrow to the pan. Stir well and bring to the boil over medium heat, then reduce the heat and simmer, stirring frequently, for 11/2 hours, or until the chutney is thick and leaves a clear trail when a wooden spoon is drawn slowly across the bottom of the pan. Take care not to cook the chutney too quickly or it will stick to the bottom of the pan.
Spoon into clean, warm, dry jars and cover immediately with vinegarproof lids. When the chutney is cold, label the jars and store them in a cool, dark, airy cupboard for two to three months to allow the flavours to mature before eating.
Zucchini, Pumpkin or Squash Chutney: Peel and deseed the pumpkin or squash as for the marrow. Zucchini only need to be trimmed before being cut into pieces. Proceed as for marrow and tomato chutney.