Prepare boiling water canner. Heat jars in simmering water until ready to use, do not boil. Wash lids in warm soapy water and set aside with bands.
NEXT, TIME TO COOK!
Combine first 3 ingredients in a 4-qt. stainless steel or enameled Dutch oven. 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 at once to boiling cherry mixture. Return mixture to a full rolling boil. Boil hard 1 minute, stirring constantly. Remove from heat. Skim foam, if necessary.
NEXT, LET'S CAN IT!
Ladle hot jam into a hot jar, leaving 1⁄4-inch headspace. Remove air bubbles. Wipe jar rim. Center lid on jar. Apply band, and adjust to fingertip-tight. Place jar in boiling-water canner. Repeat until all jars are filled.
Process jars 10 minutes, adjusting for altitude. Turn off heat; remove lid, and let jars stand 5 minutes. Remove jars and cool 12-24 hours. Check lids for seal, they should not flex when center is pressed.
DID YOU KNOW?
To guarantee the most delicious preserved foods, always begin with the best-quality produce at its peak of ripeness.