Prepare jars. Sterilize half pints or desired jars in a steam canner or boiling water. Ensure there’s enough water in your water canner and that the jars are hot. Remove carefully using jar tongs and place jars on a damp cloth.

Prepare the cherries. Wash, pit, and chop cherries into smaller pieces.

In a 4-qt. stainless steel or enameled Dutch oven add the cherries, pectin, and lemon juice. Bring mixture to a full rolling boil that cannot be stirred down, over high heat, stirring constantly.

Meanwhile, stir together sugar and cocoa until blended. Add all of it to the boiling cherry mixture. Return mixture to a full rolling boil. Boil hard 1 minute, stirring constantly. Remove from heat. Skim foam, if necessary.

Carefully ladle hot jam into hot jars, leaving ½-inch headspace. Use a non-metallic spatula or chopstick to remove air bubbles. Wipe jar rims clean with a paper towel dampened with vinegar. Place lids and screw bands, and adjust to fingertip-tight.

Place jar in boiling-water canner. Repeat until all jars are filled.

Process jars. Using a boiling water bath, process jars for 10 minutes. Make sure that the water in the water bath covers the jars by 1-2 inches. I set a timer. Processing time ensures the jam is safe for long-term storage. Remove jars carefully and let cool completely before storing.

Remove jars from the water bath and let them cool completely. Check seals after 24 hours. Check lids for seal, they should not flex when center is pressed.

Store sealed jars in a cool, dark place for up to a year. Refrigerate after opening.