Use a Jonathan or Granny Smith - something a bit tart-ish - I like to use a couple of pounds of several different apples (Granny Smith, Jonathans, Roma, and MacIntosh). I use a 5 quart crock pot (minimum size).
Place all ingredients into your crock pot, stir - if you can, cover (don't worry if the lid isn't totally on - the apples cook down) and cook about 6 hours on HIGH. Uncover, stir, use a potato masher to smush any apple chunks. Put the lid back on and cook on LOW for another 8 - 12 hours or until thickened and dark brown. If it's too thick, you can thin with a bit of apple juice.
Generally (depending on the crockpot), if you set it on high for about 15 minutes before you start to fill the jars and stir frequently, it gets to boiling. Otherwise, heat to boiling on the stovetop.
You'll also need several (8 or so) pint or (16-ish) half-pint jars with rings and lids for canning - sterilized and kept hot in simmering water - but you won't need to mess with them until about 2 hours before the butter is done.
Using a ladle, fill the jars with the boiling apple butter to within ¼-inch of the top. Wipe any spilled apple butter off the top, seat the lid and tighten the ring around them, just until barely tightened, don't go too far.
Process pint or half-pint jars in a boiling water canner for 5 minutes (follow the directions of your local county extension office). You can let them boil up to 15 minutes just to make sure with no harm to your product.
After processing, take the jars out of the water (use a jar lifter) and let them cool without touching or bumping them in a draft-free place (I set them on a dish towel-lined rimmed sheet pan overnight in my dining room). Once the jars are cool, you can check that they are sealed by verifying that the lid has been sucked down. Just press in the center, gently, with your finger. If it pops up and down, it's not sealed. If you put the jar in the refrigerator right away, you can still use it within 2 weeks - if it lasts that long.