Step 1: Prepare your canning jars and lids by sterilizing them in boiling water or a dishwasher. Keep them hot until ready to fill.
Step 2: In a large, heavy-bottomed pot or Dutch oven, combine the quartered strawberries, minced jalapeños, and apple cider vinegar.
Step 3: Bring the mixture to a simmer over medium heat, stirring occasionally, and cook for 5-7 minutes until the strawberries begin to soften. Mash lightly with a potato masher if you prefer a chunkier jam.
Step 4: Add the granulated sugar to the fruit mixture, stirring constantly until it dissolves completely. Bring the mixture to a rolling boil that cannot be stirred down.
Step 5: Stir in the liquid pectin, then boil hard for exactly 1 minute, stirring constantly. Watch carefully to prevent boil-overs.
Step 6: Remove the pot from the heat. Skim off any foam from the surface with a spoon to ensure clear jam.
Step 7: Ladle the hot jam into the prepared hot jars, leaving 1/4 inch headspace. Wipe rims clean with a damp cloth, center lids, and apply bands until fingertip tight.
Step 8: Process jars in a boiling water canner for 10 minutes (adjusting for altitude as needed). Carefully remove jars with a jar lifter and let them cool undisturbed on a towel for 12-24 hours. Check seals before storing in a cool, dark place.