Wearing gloves, slice and discard stems from peppers, then slice into 1/4-inch thick rounds. Transfer to a bowl and set aside.
In a large pot over high heat add all the other ingredients. Bring to a boil, then reduce the heat to a gentle simmer for about 5 minutes.
Add in the sliced jalapeños, bring the heat back up to high and simmer for exactly 4 minutes.
With a slotted spoon, transfer the peppers to clean, sterile canning jars to within a 1/4-inch of the upper rim of the jar.
Put the heat back on under the pot to high and boil the liquid for about 6-7 minutes. Then remove pot from the heat and let cool for about 3 minutes.
Using a ladle (or pitcher with a spout), carefully pour the liquid syrup into the jars, making sure all the jalapeños are completely submerged. (Take a chopstick and poke it into the bottom of the jars a few times to release any pockets of air.)
Wipe the rims of the jars with a clean, damp paper towel. Seal with two-piece lids. Place in the fridge.
Let chill for at least 2 weeks (preferably a month.) The longer they sit, the better they will taste.
Keep stored in the fridge and eat within 2 months. (For canning info, see notes below.)