To make plum jam, follow these general steps:

1. Prepare the plums by washing, pitting, and chopping them into quarters or smaller pieces.
2. Place the plums in a saucepan with a small amount of water and cook on medium-low heat until the fruit softens.
3. Add granulated sugar and lemon juice to the softened plums, then simmer until the sugar dissolves.
4. Bring the mixture to a rolling boil and cook until the jam thickens and reaches the setting point (about 104-105°C or 220-215°F).
5. Test the jam's setting by placing a small amount on a cold plate—if it wrinkles when pushed, it is ready.
6. Skim off any scum from the surface, optionally adding a knob of butter to disperse the froth.
7. Pour the hot jam into sterilized jars, leaving some space at the top, seal tightly, and allow to cool before storing.

Ingredients typically include plums, sugar, lemon juice, and water. The entire process generally takes about 20-30 minutes of cooking time after preparation. The jars can be sterilized by heating in an oven beforehand. This method produces a fresh, sweet, and slightly tart plum jam that can be enjoyed on bread, toast, scones, or pastries.