Heat sanitized jars in simmering water until ready to use. Wash lids in warm soapy water and set bands aside.
Prep the peppers: Wash and finely chop jalapenos (use gloves if you are sensitive). (Helpful hint: Run a teaspoon along the inside of each cut jalapeño to remove the seeds), or leave the seeds in if you like a spicy jelly.(It's a good idea to wear gloves for this step).
After hand chopping the peppers, place in a food processor or blender with 1 cup of cider vinegar. Puree until smooth. Do not strain.
Combine pepper puree in a large saucepan with sugar & remaining cup of apple cider vinegar- stirring constantly
Bring the mixture to a boil over high heat stirring constantly. (Don't leave the stovetop during this stage as this mixture WILL foam up and over the top unless you are careful). Just as it starts to come to a boil, lower heat and with a ladle, skim off any foam. Then, increase the temperature to a point where it will gently boil, but not rise up and over the top.
Boil for 10 minutes - while whisking, add liquid pectin and boil hard for an additional minute. Remove from heat, skimming any additional foam if necessary.
Ladle hot jelly into sterilized hot jars leaving ¼ inch headspace. Wipe rim. Center lid on jar. Apply band until fit is fingertip tight.
Process in a boiling water canner for 10 minutes. Transfer jars to a towel-lined surface and let rest at room temperature until set. After 24 hours, check seals (Lid should not flex up and down when pressed in centre). Refrigerate any unsealed jars for up to 3 weeks.