Preparing the juice:
Clean choke cherries. (no need to remove pits) Put in large kettle and cover with water. Boil 15 to 20 minutes. Strain cooked berries through cheese cloth. You might need a few layers of cheese cloth. To strain juice through the cheese cloth there are several methods. Method 1) I like to tie the ends of the cheese cloth together and thread a long wooden stick just under the knot and suspend it over a deep pot. The pot should be deep enough so the hanging cheese cloth does not touch the gathered juice at the bottom. Just let the juice drain overnight. If you are in a hurry, and don't mind a potential mess, you can use the stick as a press and while holding the hanging cheese cloth, slowly start to turn the stick. The cheese cloth will begin gather in and the juice will be forced out. Note: I have done this where I have twisted too fast and it created too much inward pressure, creating a hole in the cheese cloth and a mess. Method 2) Suspend a large colander from the lip of a pot, line the colander with cheese cloth, strain the cooked berries through the cheese cloth supported by the colander. Let the juice drip, when done dripping the juice is ready to make into jelly.
Making the jelly:
Prepare your jars and lids. Jars need to be very clean. The lids with the seal should be placed in a pan and have boiling water poored over them to help sterilize. Keep the lids in the hot water until used.
Measure 3 1/2 cups prepared chokecherry juice into a 6-8 qt. pot.
Stir in pectin. (you may add a dab of butter to help reduce foaming) On high heat, stirring constantly, bring to a rolling boil. (a boil that doesn't stop bubbling as you stir) Stir in the sugar. Return to rolling boil, stirring constantly, then boil one more minute. Remove from heat. Remove any unwanted foam from the top of the mixture.
Ladle immediately into prepared jars. Fill the jars so the jelly is about 1/4 inch from the top. Make sure the jar rim is clean and wipe off any jelly that might have been dripped on the jar rim. Cover with a lid from the hot water and screw on the outer threaded band tightly. Place jars in canner. Make sure there is enough water to cover the tops of the jars by an inch of two of water. Bring water to a boil. Process for 10 minutes. Remove from heat and place jars on a towel or cooling rack to cool. When the jars have completely cooled, check the seal by pressing the middle of the lids with your finger. If the lids pop up, they have not sealed and you will need to refrigerate the jars.