• 1.5kg fresh raspberries
• 1kg granulated sugar (adjust when you weigh the fruit pulp)
• 1 lemon

Check over the raspberries and discard any with signs of spoilage. Give the fruit a rinse and place in a heatproof bowl. Warm the fruit in a low oven for an hour.

Wash the recycled glass jam jars and new lids. Let them dry in the low oven.

Meanwhile, sieve out the seeds. A food mouli makes easy work of it. Weigh the fruit pulp and adjust the amount of granulated sugar.

Place the fruit and sugar in a maslin pan and heat gently. Stir until the sugar has dissolved. Add the juice of a lemon and bring everything to a boil.

After about 5 minutes a sugar thermometer will read 105ºC (or thereabouts).

Skim off the scum. A small knob of unsalted butter, stirred through in a clockwise direction will deal with any remaining.

Pour into the sterilised jars, taking the jam to within a few millimetres of the rim. Immediately cover with the sterilised lids and lightly screw on. Tighten when cool. Then label.

Eat.