Prepare lids and jars as directed by manufacturer. Keep warm.
Prepare fruit by crushing berries 1 cujp at a time using a potato masher. If using a food processor, pulse to chop do not puree. Jam should have bits of fruit in it!
Note - make sure you take the stem out of the mullberries and wear gloves unless you want pretty bed hands.
Once your fruit is crushed put it in a 6 to 8 quart saucepot.
Measure your sugar in a separte bowl. Add sugar to crushed berries. Add 1/2 teaspoon butter, optional to help reduce foaming.
Bring mixture to full rolling boil on high heat stirring constantly. Once mixture comes to a rolling boil add the pectin quickly. Return to a full roilling boil and boil exactly 1 minute stirring constantly. Remove from heat and skim off foam with a metal spoon.
Ladle quickly into your prepared jars filling to within 1/8 inch of tops. Wipe off rims and threads cover with two piece lids. Screw bands tightly and place in your canner. Water must cover jars by 1 to 2 inches; add boiling water as needed. Cover and bring water to gentle boil. Process for 10 minutes. Remove jars and place upright on 2 thick towels and coool completely.