4 cups mashed strawberries
4 cups sugar
1/4 cup lemon juice
Stir all together in a large pot cooking over medium-high heat. Bring to a boil and stir constantly until it reaches 220 degrees. This will probably take at least 10 minutes of hard boiling. You can use a candy thermometer or use the freezer plate* method to know if you are ready to can it. Once it reaches the jelling point fill hot sterilized jars leaving 1/4" head space (space between the top of the jelly and the top of the jar. Put into the hot water bath and bring to a boil. Once boiling process (with lid on) for 6 minutes. Remove from water bath and let cool. Listen to the pops that tell you that you have successfully canned strawberry jam!
*The freezer plate method is very cool, especially for those of us without candy thermometer. You put a few small plates in the freezer and when you think the jam has boiled enough you put a small puddle on the cold plate. Let it cool a moment and run your finger through it. If it stays separate and doesn't run back together it is ready to use or can. If it is too runny it needs more time. Keep stirring and boiling and try again!