BASIC STRAWBERRY JAM
2 pounds ripe strawberries (a little less than 2 quarts)
2 1/2 cups sugar (a little less will lead to a softer set)
1 tablespoon freshly squeezed lemon juice
Optional: a few scrapings of lemon zest
Briefly rinse the berries and remove their caps. Combine with the sugar, lemon juice, and zest, if using, in a large bowl, and crush with a potato masher (or your hands).
Turn the fruit-sugar mixture into a preserving pan, and bring to a boil over high heat, stirring regularly. Reduce at a full rolling boil, stirring all the while, to the gel point, 8 to 10 minutes (mine took about 14), depending on the size of your pan and the strength of the heat source.
Once a gel set has been achieved, skim if necessary, and ladle the hot jam into four prepared 1/2-pint jars, leaving 1/4 inch head space. Seal, and process in a boiling-water bath for 10 minutes.
Notes: The sugar content in this recipe is lower than in many traditional farmhouse recipes, but there’s still enough for a soft-set consistency and to ensure a reasonably long shelf life once opened.
Also, do not double the quantities, at least not initially. A small batch is cheaper, faster, more manageable, and better suited to the size of standard household equipment. If you want more jars, make two small batches. I can assure you from personal experience that you’ll be happier with the outcome. In fact, the more experienced I get, the more I’m inclined to do three or four jars at a time — a nice little job to knock off in an hour, rather than a labor that wrings the fun out of the afternoon.
From Kevin West’s Saving the Season, as heard and read on NPR.