1-1/2 lbs. firm-ripe plums, cut into 1-in pieces (with skin)
2-1/4 C. sugar
2 Vanilla beans, split lengthwise and halved crosswise
4 small cinnamon sticks
1 lemon
1-1/2 lbs. firm-ripe plumcots or apricots, cut into 1-in pieces (with skin)
1. Put the plums, sugar, vanilla beans and cinnamon sticks in a large, wide saucepan. Squeeze the lemon juice through a strainer into the pan. Cook over med-high heat, stirring occasionally, until the sugar dissolves and the mixture boils, about 10 minutes.
2. Reduce heat to med and continue to cook, stirring occasionally, until a candy or deep-fry thermometer registers 220, about 30 minutes. To be sure the mixture has reached the gel point, spoon a small amount on a chilled plate and put in the freezer until cook. The liquid should set; if not, continue to cook and retest after a few more minutes. Remove the pan from the heat and let cool 30 minutes.
3. Meanwhile, sterilize four 8-oz canning jars and lids.
4. Return the plum-mixture to med-high heat. Bring to a boil, stirring, then add the plumcots. Reduce the heat to medium and simmer until plumcots are tender, about 5 minutes. Discard the cinnamon sticks.
5. Fill the jars with the plum mixture, leaving 1/2 inch headspace, then seal and process 15 minutes in a water bath.