To make the chicken: Scatter the onions on the bottom of the slow cooker and drizzle with 1 tablespoon of the olive oil. Put the chicken breasts on top, and poke several times with a fork, then sprinkle with salt.
Add the remaining oil and the chipotles with their sauce. My family loves the spice, so I use the whole can. If you want your chicken more on the mild (but still delicious) side, use half the contents of the can and save the rest. Make sure the chicken is well coated.
Close the pot and set it for as long as you can. I try to get it going right after breakfast and set it for 8 hours, which yields very tender chicken that pulls apart with the touch of a fork. 4 hours will get the job done in a pinch, but you’ll end up with larger pieces that won’t be quite as fall-apart tender.
When the time is up, open carefully to let the steam escape. Using tongs or a fork, remove the peppers and discard. Use a ladle or large spoon to remove about a cup of the liquid from the cooker. Then use two forks to shred the chicken. It should be very very tender and shred easily. Taste and adjust the salt and pepper, if you like. Keep warm in the slow cooker until you’re ready to serve, adding a bit of the reserved liquid if it starts to get dry.
To make the slaw: Combine all ingredients in a large bowl and toss to combine. Let it sit for 10 minutes or so if you can before serving to let the flavors come together.
Assemble and serve: Use small flour or corn tortillas. My family members eat an average of 3 tacos each, but admittedly we have big appetites. Do your own math. I usually buy a 10 count package of each so we’ve got tortillas for leftovers the next day.
Warm the tortillas slightly in a low oven for a few minutes before serving. Set everything out on the table and have at it. Garnish with crumbled goat cheese, sliced scallions, and cilantro.