In a large bowl, stir together yogurt, mayo, dip mix, vinegar, sugar, salt and pepper. Thinly slice cabbage. You should have about 5 cups. Add to bowl; stir to combine. If making ahead, keep refrigerated, up to 3 days.
Slice onion. Slice buns open and toast, if desired.
Fill each bun with pork; add 1/4 cup coleslaw to each sandwich. Top with onion. Serve with remaining coleslaw on the side.
For added tang and freshness, give the red onion a little more love. Add sliced red onion to a large bowl. Squeeze in juice from 1 lemon, then add a pinch each of sugar and salt. Using your hands, gently toss and squeeze onion to help soften it slightly.
