Make the pork by placing onions and garlic on the bottom of the slow cooker. Liberally season pork steaks with salt and pepper. Place steaks on top of onions. Spoon chiles over the top. Pour water around the meat. Cover and cook on the slow cooker's high setting for 4 - 5 hours.

To make the slaw whisk together mayonnaise, cilantro, lime juice, salt and cumin together in a bowl. Mix in cabbage. Toss to coat. Cover and refrigerate for at least 30 minutes.

Once pork has cooked remove from slow cooker. Reserve chiles. Remove bones. Shred pork and mix together with chiles. Cover to keep warm.

Combine flour, salt, chili powder and garlic in a resealable plastic bag. Place onions in bag and toss to coat.

Heat 1/4 - 1/2 inch oil in a skillet over medium-high heat. Sprinkle flour in oil and if it sizzles it's ready.

Remove onions from bag, shake off excess flour and use your hands to separate onions. Fry, in batches, until golden brown and crispy, about 2 minutes. Use tongs or slotted spoon to transfer to a paper towel lined plate. Sprinkle with salt.

Assemble the sandwich by spooning pork on bottom bun, top with slaw, onion strings and top bun. Serve.