Start with our step-by-step canning how-to.
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 medium-high heat, stirring occasionally, until the sugar dissolves and the mixture boils, about 10 minutes.
Reduce the heat to medium and continue to cook, stirring occasionally, until a candy or deep-fry thermometer registers 220 degrees F, about 30 minutes. (To be sure that the mixture has reached the gel point, spoon some onto a chilled plate and put in the freezer until cool. 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.
Meanwhile, sterilize four 8-ounce canning jars and lids.
Return the plum mixture to medium-high heat. Bring to a boil, stirring, then add the plumcots. Reduce the heat to medium and simmer until the plumcots are tender, about 5 minutes. Discard the cinnamon sticks.
Fill the jars with the plum mixture, leaving 1/2 inch headspace, then seal and process.
Photograph by Charles Masters
Recipe courtesy of Food Network Magazine