Blackberry Jam with Fresh Lemon Juice

Instructions:

1. Place the rinsed blackberries in a heavy-bottomed pot and use a potato masher or the back of a large spoon to lightly crush the berries.
2. Stir in the granulated white sugar, fresh lemon juice, and butter.
3. Turn the heat to medium-high and bring the mixture to a rolling boil, stirring constantly to prevent the sugar from sticking to the bottom.
4. Maintain the boil until the mixture reaches 220°F (104°C) on a digital candy thermometer, which typically takes 20-30 minutes.
5. Carefully ladle the hot jam into sterilized half-pint jars, leaving 1/4 inch of headspace.
6. Wipe the rims clean and seal tightly. For long-term storage, process in a boiling water bath for 10 minutes; otherwise, cool and store in the refrigerator for up to 3 weeks.