1. Place a few small plates in the freezer. Stir together berries, sugar, lemon zest and juice, salt, and bay leaves in a large, heavy stockpot. Bring to a boil, stirring to dissolve sugar and mashing lightly with a potato masher. Skim foam from surface. Cook, stirring more frequently as jam thickens, until it is the consistency of very loose jelly, 10 to 11 minutes. Remove pot from heat.

2. Press about half of the jam through a medium sieve; discard seeds. Return strained jam to pot, and stir until combined. Return to a boil.

3. Remove a plate from freezer, and drop a spoonful of jam on it. Return to freezer for 1 to 2 minutes, then gently nudge edge of jam with a finger. If jam is ready, it should hold its shape. If jam is too thin and spreads out, return to a boil, testing every minute, until done. Remove bay leaves, and discard. Spoon hot jam into hot sterilized jars, and cover immediately with sterilized lids.